Toshinori Yagi/Synopsis

History
Before meeting his teacher, who had passed on One For All to him, Toshinori originally did not have a Quirk. Five years before meeting Izuku, Toshinori fought a very powerful villain known as Sensei, who used a Quirk known as "All For One", which resulted in critical injuries that set a limit on the usage of his quirk.

Entrance Exam Arc
All Might first appears spotting the Sludge villain fleeing after robbing a bank. He tracks the villain through the sewers and eventually finds him trying the seize the body of a young man, Izuku Midoriya. All Might uses his Texas Smash to blast the villain apart and save Izuku. While the young man recovers, All Might encases the villain inside a couple of empty bottles, in order to take him to the authorities. When Izuku awakens, he finds that All Might has signed his notebook and thanks him. All Might prepares to leave, but the young fan boy holds on to All Might after he leaps high into the air. All Might is forced to land and tries to leave again, but Izuku questions him on whether he can become a Hero without a Quirk. Before answering, All Might reverts to his true form, shocking Izuku.

All Might reveals to the young man that he was injured in battle five years ago and can only stay in his hero form for a short time. He goes on to tell Izuku that professionals must always put their lives at stake to save the day and thus cannot openly say whether it is possible to be a Hero without a Quirk as it may not be possible. All Might says that if Izuku cares about saving people, he can always go on to become a policeman, as in that way he can be responsible for putting the villains in jail (even though it is ridiculed). He tells Izuku that it is not bad to dream, but warns him not to obscure the facts and then leaves.

After leaving, All Might notices that he wasted time in talking with the young man, giving the villain he defeated a chance to escape, ridiculing himself for making a rookie mistake. He makes his way to the scene of the crime, where the Sludge villain has captured yet another young man, Katsuku Bakugo. He is unable to intervene after using up his hero form, but after seeing Izuku's bravery in trying to save Katsuki from the villain, All Might is inspired enough to step in and use Detroit Smash to defeat the villain, saving both young Izuku and Bakugo. All Might is swarmed by reporters after the battle.

Later on that same day, All Might  appears before Izuku, thanking him and giving him a proposal. All Might tells Izuku that he was touched by his bravery for trying to save someone despite not having a Quirk and tells him that he too can become a hero.

All Might reveals to Izuku that his Quirk can be passed down and that Izuku has been chosen by him to be the next one to inherit his Quirk. Izuku asks why he would give someone like him his Quirk, to which All Might responds that he has been searching for a successor for a long time and now has found someone that he doesn't mind giving his Quirk to, saying that he despite not having a Quirk,  Izuku tried to save young Katsuki while other people and heroes stood idly by. Izuku accepts All Might's proposal and they begin training for the next ten months, explaining to him that in order for him to inherit his Quirk, Izuku's body (vessel) must be strengthened to the point of being able to handle the One for All's power.

All Might trains Izuku at the Seaside Park, a coastline that has been filled with trash. He has Izuku clean up all the trash as part of training his body to become stronger. After 10 months have passed, Izuku becomes a genuine vessel and All Might rewards his hard work by having Izuku consume a piece of his hair, enough DNA to transfer One for All to Izuku.

All Might takes part viewing the entrance exam. He is pleased to see that Izuku was willing to sacrifice himself to save Ochaco Uraka. After Ithe exam finishes, All Might finalizes the paperwork to become U.A. faculty member. He delivers Izuku's test results via holographic video. He first apoligizes for not speaking to Izuku in the week after the exam. He continues, telling Izuku he did fine on the written exam and got zero combat points during the practical. However, he goes on to explain that Izuku's brave actions during the exam were enough to score him sixty rescue points, giving him more then enough points to get accepted into U.A. Highschool.

Quirk Apprehension Test Arc
All Might is seen secretly inspecting Izuku's participation in the pitch trial of the Quirk Apprehension Test, impressed with Izuku's focus of the One For All Quirk at the tip of his finger and for his quick thinking of using the One For All Quirk in the shortest time possible at the last moment as a workaround for not being adjusted to the Quirk. All Might approaches Shouta, calling him a liar and says that he once expelled an entire new class of first-graders last year. All Might knows that he kicks students out with zero chances, finding it weird that he did not expel Izuku on the spot and concludes to him that even he felt Izuku's raw potential. However, Shota replies that Izuku's are above the "zero" mark and that is all. He continues to say that he can kick anyone out whose chances drop below that mark at any time, then leaves. All Might then says that they will never get along. All Might then appears as the teacher of the foundational hero studies, saying that they will have a battle of trial for the period. He tells his students that U.A. have prepared their Hero Costumes and says to them to get changed into their costumes for the battle trial.

Battle Trial Arc
All Might explains to his students that they will be separated into Heroes and Villains for the battle trial and it will be a two on two team battle. He explains that in the battle trial, the villains will guard a nuclear weapon they intend on deploying and the heroes must stop them. He goes on to further say that the heroes can win by capturing the villains or reach the nuclear bomb before time runs out and the villains can win by capturing the heroes or keeping the core away from the heroes before time runs out. All Might then decides that the teammates and pairs will be chosen by lottery. After the lottery, All Might draws from the boxes and says that the pairs that will do battle are the heroes: Izuku and Ochaco versus the villains: Katsuki and Tenya. He explains that the villains will go in the building first, then after five minutes, the heroes will go in. He tells them to go all out as it is a practical exercise, although he says that he will stop the battle trial if things get out of hand. All Might is seen in the surveillance room, saying to himself that Izuku won't get any special treatment from him and will grade him as harshly as the rest. All Might tells Katsuki to stop after seeing what his Hero Costume can do to amplify his Quirk and becomes worried for Izuku after Katsuki initiates a huge explosion.

All Might then tells Katsuki that if he uses another huge explosion, he will end the battle trial and he will lose, reprimanding him for trying to destroy the building that protects their stronghold (the core) calling it foolish. Although he feels that he should stop the battle trial, he thinks that it would be better for Izuku and Katsuki to continue battling as it is necessary for the future that they envision themselves. After being asked to stop the battle trial, All Might is about to suspend it, but after hearing Izuku call out to Ochaco, he stops. After Ochako touches the core, All Might announces that the Hero team wins.

All Might approaches Katsuki, telling him that it is time for his critique. He tells Katsuki that it does not matter whether he won or lost, but that he takes one look back, reflect on his experience and move on with life. In the monitor room, All Might says that Tenya was the best during the battle trial. After being asked why, he questions his students as to why he chose Tenya. After Momo Yaoyorozu gives her answer, he gives a thumbs up to her for being absolutely correct. During the next battle trial, All Might is impressed by Shoto Todoroki for not getting his comrade caught in the attack and at the same weakened his opponents' positions as well as refrained from damaging the core. After everyone participates in the battle trial, he tells everyone that they did well and instructs them to change clothes and head back to class. Although he wanted to give Katsuki counseling for his self-confidence, he realizes that his transformation is running out of time and head to the nurse's office.

He is reprimanded by Chiyo Shuzenji for indulging his disciple, Izuku, too much and he says that he has nothing in his defense. They talk quietly, with him saying that his Quirk is secretly known by a selected few (including her). Chiyo asks if it is important to be a "Natural Born Hero" or "The Symbol of Peace" to which he replies that without such a symbol, the society of superhumans would fall to evil. She then tells All Might to be a better guide to Izuku. All Might then appears before Katsuki, trying to counsel him on self-confidence, although he is told in response by Katsuki that he will surpass him as well, thus All Might decides to leave Katsuki alone, finding that teaching can be difficult.

Unforeseen Simulation Joint Arc
All Might is seen using Missouri Smash on Vihara Headgear, defeating him and saving the family in the process. He then realizes that his Quirk is steadily dropping off, as the amount of time he can keep his Quirk activated has decreased. In a flashback, Izuku is seen speaking to All Might telling him that he revealed to Katsuki about the secret of the One For All Quirk. However, All Might is not angry about it since Katsuki interpreted it as nonsense and tells Izuku to keep the secret to himself and no one else since if the villains knew about his secret, all of them would probably want to steal his Quirk. He then tells Thirteen that he will not be able to appear at the Unforeseen Simulation Joint due to him using his Quirk too much and then takes a nap. After his nap, All Might tries to contact, Thirteen and Shota, but to no avail. He decides to go to the U.S.J, but Mr. Principal arrives to have a discussion with him, being held up by Mr. Principal's endless talking, seeing that he has not changed either. All Might then appears at the U.S.J, telling everyone to have no fear as he is there.

He says that he ran into Tenya and knows the gist about the situation. All Might quickly dispatches the villains in front of Shota, apologizes to him and picks him up. He then rescues Izuku, Minoru, and Tsuyu. All Might asks the three to head to the entrance and leaves Shota with them. When Izuku tries to dissuade him into fighting, Al Might tells him it is all right. All Might uses Carolina Smash on Nomu, but has little effect. He realizes that his blows are not having any effect against the villain. After hearing Tomura's information on Nomu, All Might uses a backdrop slam against Nomu, causing an explosion. However, Kurogiri opens a gate with his Quirk, causing All Might's attack to fail and allows Nomu to grab All Might. However, the combined efforts of Katsuki and Shoto allow him to escape from Nomu.

All Might then blocks a punch from the regenerated Nomu, giving Katsuki some time to evade. All Might then calls Tomura's view on the title Symbol of Peace as rubbish. He then tells the children to escape, thanking Izuku for his concern and says that he is fine. Realizing that he has only a little time left, All Might decides to go all out. He and Noumu get into a fist fight and All Might sees that he can absorb each punch at 100%. All Might decides to surpass his 100% and launches a devastating punch against Nomu, sending Nomu flying out of the U.S.J, defeating him. In his younger ages, All Might claims that it would have taken five punches top to defeat someone like Nomu but now that he is not in his prime self anymore, it took over 600 punches. Even though he is badly beaten and battered, All Might prepares to fight Tomura.

All Might asks why he is not going to fight since it is his mission to kill him. All Might then realizes that his fight with Nomu has completely left him powerless, not even having the strength to take another step. Tomura and Kurogiri attack All Might, but Izuku intervenes to protect the powerless All Might. However, one of the heroes that Tenya called as backup stops Kurogiri and Tomura from attacking him. When Izuku says he could not do anything, All Might says it is not true, telling him that if it were not for his few seconds of bravery, he would be dead and thanks him for saving him.

All Might is then seen at U.A.'s Nursery, being treated by Chiyo. A detective arrives who All Might knows and asks him about the students' conditions, as well as Shota and Thirteen. The detective tells him that the students are unharmed, but Shota and Thirteen are injured, but not in danger of death, relieving All Might worries. All Might tells the detective that the students fought bravely and that they will become great heroes, to which the detective agrees.

Sports Festival Arc
All Might is seen in the meeting room, commenting on Tomura's arrogance and when he started to panic when things went wrong. After taking Tomura's childish personality into consideration as well as his determination, All Might concludes to those in the meeting room that Tomura is a mere character who believes that he is the center of attention, an "adult-child". After the meeting, All Might finds Izuku and asks him to have lunch with him. In the resting room, All Might asks him how he is handling his Quirk and Izuku replies that he has gained adjustment to the Quirk, saying that he did not break his arm when punching Nomu, which pleases All Might.

He then tells Izuku that his time as the Symbol of Peace is heading to an end, much to Izuku's sadness. All Might says that U.A.'s Sports Festival is an event the whole country will be watching and tells Izuku that in the event he wants the whole world to know that he is the new generation's "All Might" and the future Symbol of Peace, shocking Izuku.All Might states that he wants Izuku to demonstrate his full potential to everyone at the Sports Festival. After Izuku doubts himself, All Might encourages him, stating that the difference between someone who aspires to the top and someone who does not will have a huge influence when he steps up and steps forward in society. All Might says that he understands Izuku's feelings towards his condition and will not force him to do anything, but asks him to remember his feelings during the time he cleaned up the Seaside Park.

At the Sports Festival, after Izuku places first in the Obstacle Race, All Might smiles and claps for him. All Might then ponders about Katsuki, thinking that his ranking in the Obstacle Race, combined with the sheer versatility of his Quirk makes him a popular choice for a teammate. Near the end of the Human Cavalry Battle, after seeing Katsuki using strategy to get Neito's last headband, All Might comments to himself that Katsuki, despite no one telling him, is grasping instinctively the difference between those who do not necessarily aim for the top all of the time and those who always do.

After the lunch break begins, All Might in his hero form greets Enji Todoroki, saying its been a while and asks him to have tea with him. All Might says that they have not spoken to each other in ten years and that he wanted to give him a shout out, Enji replies that he can take his tea offer to some other place and tells him to go away. As Enji leaves, All Might stops him, saying that his son Shouto was able to show a great performance even without using half of his power. All Might then asks Enji for advice on how to raise the next generation. Enji comments on All Might's attitude, finding it to be annoying and then says that he will make Shoto a hero that surpasses All Might, then angrily walks away.

All Might goes to see Izuku before the beginning of his match. After Izuku says that he can raise his strength only a little with One For All, All Might says that originally, on a scale of one to a hundred, the amount of strength Izuku's body could tolerate it was zero, but now it is a five.

When Izuku starts frowning, All Might cheers him up; telling him to do his best and encourages him to smile when he is full of fear and anxiety. All Might then concludes that he is always watching Izuku.

All Might goes to the infirmary to see Izuku. After Chiyo scolds All Might for putting pressure onto Izuku, Izuku tells All Might about the mysterious shadows he saw, saying that the shadows helped him break free of Hitoshi's mind control and asks All Might if what he saw were the people who wove the power of One For All. All Might replies that he too saw something similar to what Izuku saw in his younger days. All Might theorizes that the people he saw were imprints of those who have used One For All but not the sort who have a will on their own and concludes that Izuku broke Hitoshi's spell, not because of the predecessors of One For All but because his unwilling of willpower caused the vision to appear that broke Hitoshi's brainwash.

Izuku isn't completely satisfied with the explanation, but All Might tells Izuku not to dwell on it and tells him to go watch the next match. After Izuku leaves, Recovery Girl says that Izuku also saw him in the vision, to which All Might replies that it is a good thing.

During the match between Izuku and Shoto, All Might watches on, worried for his student's health. After Izuku states to Shoto that becoming Number One without his full strength as well as to disown someone is a joke, All Might remembers Endeavor's words of making his son surpass him. Soon after remembering, All Might theorizes to himself that Shoto won't use his fire power due to the discord between him and his father. He then tries to figure what Izuku is trying to do. After Shoto activates his fire power, All Might concludes that Izuku is trying to save Shoto from his cruel fate, despite wanting to win. All Might notes that Izuku is going out of his way to help his opponent, causing him to wonder which of them is the joke.

After Izuku is defeated by Shoto, All Might goes to Chiyo's office to see Izuku. She scolds All Might for making Izuku push his limits and tells All Might not to try and praise Izuku for going so far. When Izuku apologizes to All Might for not living up to his expectations, All Might's face is filled with regret. After Izuku tells All Might that all he wanted to do was help Shoto and asking for forgiveness, All Might responds by saying that his match was simply an unfortunate outcome but praises Izuku for helping Shoto with his problem, saying that reaching out and helping people with their personal problems is one of the principal qualities of a Hero, happy that Izuku has such a quality.

After Izuku's surgery is finished, Chiyo tells All Might to try and find a different method for Izuku to use his One For All. Izuku leaves Chiyo's room with All Might and they walk down the corridor. Izuku sadly tells All Might that he thinks someone else should be his successor. However, All Might tells Izuku that he used to be Quirkless just like him, which surprises Izuku. Izuku says to All Might that he never knew about that information causing All Might to reply that Izuku never asked him. All Might tells Izuku that he chose him to be his successor at first due to him being similar to his former self and admits to Izuku that he has surpassed his expectations after seeing Izuku's actions. He then says to Izuku that only he will be able to truly shine with the power of One For All. Having been cheered up by his mentor, Izuku apologizes to All Might. All Might tells him to watch the rest of the Sports Festival, to which he complies.

All Might, in his Hero form, appears at the closing ceremony of U.A.'s Sports Festival to hand out medals to the winners of the Freshmen Stage: Fumikage, Shouto, and Katsuki. All Might gives Fumikage his medal for placing third, congratulating and acknowledging his strength. He gives Fumikage a pat on the back and a congratulatory hug, telling Fumikage that in order to defeat his problem with unfavorable matchups he should not always rely on his Quirk and that he should increase his own strength to deal with unfavorable matchups better. All Might gives Shoto his medal for placing second, congratulating him and understands that Shoto had his reasons for suppressing his fire side in the final match. After Shoto tells All Might that he must come to terms with things to solve his problems, All Might gives Shoto a congratulatory hug, saying to Shoto that he will not pry any further and that he knows fully well that Shoto can solve anything with his power. All Might then goes to give Katsuki his medal for first place, finding the restraints to be a little too much. All Might takes Katsuki's face mask off, causing Katsuki to angrily yell that he does not deserve to be Number One. However, All Might tells Katsuki that society will acknowledge him as Number One even if he does not. All Might gives Katsuki his medal. Afterwards, All Might gives a speech to everyone, saying that everyone who participated in the Sports had a chance to stand on the podium. He goes on to say that the future generation of heroes looks bright. All Might yells out "Great Work", much to the confusion of the crowd who thought he would yell "Plus Ultra", causing him to reply that he thought "Great Work" would be far more appreciative.

Vs. Hero Killer Arc
All Might is in U.A.'s Faculty room. Ken informs All Might that a new nomination has just arrived for the freshmen, telling All Might that the nomination is for Izuku. Excited, All Might goes to check who nominated Izuku. As he checks, All Might becomes flabbergasted at the person who nominated Izuku.

After school that day, All Might appears in front of Izuku as he is about to leave class. All Might and Izuku walk along the corridor. All Might says that Izuku received a nomination, much to Izuku's surprise. All Might tells Izuku that the person who nominated him was Gran Torino. All Might explains that Gran Torino was a Pro Hero who taught at U.A. for one year and that Gran Torino was his homeroom teacher. All Might says that Gran Torino was a close friend of his predecessor, but now he is in retirement. All Might says that Gran Torino knows about the One For All Quirk which is the reason why he must have nominated Izuku. Shaking nervously, All Might wonders if Gran Torino was compelled to nominate Izuku due to him thinking that his guidance towards Izuku was lacking, becoming terrified by the fact that he is taking up his Hero Name again. While trying to stop his legs from shaking, All Might tells Izuku that while it is his duty to train him, he should select Gran Torino as his work place of choice and see what he can learn from him. Before leaving, All Might informs Izuku that his Hero costume has been repaired.

Naomasa meets with All Might at U.A. He tells All Might that the Police Force has tried everything to get information out Nomu; however, everything they tried did not work. Naomasa says that they instead looked into Nomu's background through DNA analysis and have discovered that Noumu was once a human with a criminal record. Naomasa explains that the DNA analysis also revealed that Noumu has the DNA of at least four different humans mixed with his own. Naomasa concludes that Nomu is an artificial human made to measure up to multiple Quirks and that having all the DNA in his body as well as his body modified caused Nomu's brain activity to stop. Naomasa tells All Might the real issue is that Noumu's DNA is of primary concern because it contains multiple Quirks. Naomasa says that Noumu could not have acquired multiple Quirks in any way (unless Nomu acquired the Quirks through advanced genetic familial permeation.) Naomasa comes to the conclusion that someone with a Quirk that can grant Quirks is behind Noumu's acquisition of multiple Quirks. All Might becomes concerned.

After Stain's defeat is published, Gran Torino speaks to All Might using a telephone. Gran Torino expresses his annoyance that his pay has been cut in half and his right to teach is revoked for half a year but says that considering the circumstances he does not mind. Gran Torino tells All Might that Izuku has improved drastically in using One For All, saying that Izuku movements are similar to his own; All Might apologizes profusely and thanks Gran Torino for his help, admitting that his teaching towards Izuku has been inadequate. Gran Torino says that he only became qualified as a teacher so that he could keep his promise to Shimura, All Might's predecessor. All Might thanks Gran Torino for everything as he wouldn't be the man he is today without him; Gran Torino yells that All Might forgot about him, to which All Might says that he never forgot. Gran Torino tells All Might that he is calling him about the encounter with the Hero Killer; he admits that Stain's strong ideology is similar to All Might's. Gran Torino says that if Stain's backstory is revealed to the public through the use of media, villainy will rise and the Villain Alliance will take credit as a group following Stain's ideology due to the connection between them which will cause delinquents to join the League of Villains. Gran Torino states that he believes that an old enemy will use Stain's backstory to remove obstacles in his path. Gran Torino hypothesizes that the old enemy, the villain who killed All Might's predecessor and gave All Might his scars, "All For One" has returned. All Might is in disbelief that "All For One" has returned, not wanting to believe it. Gran Torino advises All Might to reveal to Izuku everything about himself and One For All when the opportunity arises.

The workplace training comes to an end and Class 1-A returns to U.A.. Class 1-A next class is Foundational Hero Studies with All Might. All Might says that their lesson will be a rescue training race through Playing Ground Gamma (a construction site with many densely packed lanes which makes it look like a labyrinth). The class must race through the construction site and to the area in the middle to meet up with All Might. Class 1-A will split into four groups of five for the training lesson. Izuku, along with Ojiro, Tenya, Mina and Hanta are the first group that will partake in the rescue training race. All Might watches the race and is surprised at Izuku's movements. After the race ends, All Might commends the group on improving their Quirks more broadly since entering U.A. He asks them to prepare for the end-of-term test. All Might then approaches Izuku, telling him that he is impressed with his improvement and gives him a thumbs up. All Might tells Izuku that after the lesson is finished, he should come to his place because he wants to talk to Izuku about the story of him and One For All.

All Might meets with Izuku in the Break Room. All Might tells Izuku to lock the door and then apologizes to Izuku for not being at his side during the Hosu incident, to which Izuku replies that he does not have to apologize. All Might says that Izuku's blood was ingested by the Hero Killer, reminding Izuku about One For All transfer and inheritance method, causing Izuku to panic (thinking that One For All is in Stain's possession). However, All Might tells Izuku that he still has One For All because One For All will not be transferred to a new recipient unless the user wishes it, thus One For All cannot be forcibly stolen, although it can be forcibly passed on. All Might tells Izuku that One For All is a special Quirk and begins telling izuku One For All's origin. All Might says that One For All is derived from a Quirk that has existed since the beginning.

All Might says that long ago during the Quirk phenomenon, society had not adapted to the idea of having Quirks which caused an age of upheaval to arise; a man possessing a Quirk called All For One (a Quirk that can steal Quirks and grant them) stole many Quirks and used his new overwhelming power and influence to gather and unify people under his command. The man used the people he gathered as pawns for his plans which allowed to take over Japan and made himself its evil ruler. Izuku says that he has heard rumors but this story is not in any textbook causing All Might to reply that underground dealings are never recorded in the textbooks. Izuku asks how this man is related to One For All. All Might says that All For One can grant Quirks, but those who were not able to handle the strain became brain-dead like Noumu. All Might explains that there were cases for those who did survive the procedure where their Quirks mutated. All Might tells Izuku another story; the man (who would eventually become Japan's evil ruler) had a younger brother; the man used All For One and forcibly gave his younger brother a Quirk that stockpiles power. However, the younger brother already had a Quirk, a Quirk that can transfer itself to others. The younger brother's Quirks (one that stockpiles power and the other that can transfer itself) merged and became One For All.

All Might notes the irony that justice was born in the bowels of evil. Izuku says that it is impossible for the man who ruled Japan in the distant past to be alive. All Might theorizes that the man stole a Quirk that stopped his aging or a Quirk that granted him immortality. All Might explains that the younger brother, whose Quirks became One For All, fought against his older evil brother but could not defeat him. The younger brother decided to pass on One For All to the next generation so that one day it will accumulate enough power to defeat the older brother's All For One; All Might says that he was finally the successor that defeated the older brother, or so he thought. All Might tells Izuku that the man possessing All For One has returned and is leading the League of Villains. All Might finishes his story by saying that One For All is a power that is meant to stop All For One and that Izuku will also have to confront the man.

All Might apologizes for giving Izuku so much information. Izuku says that whatever task All Might gives him he will accomplish no matter what as long as All Might is by his side. All Might is not able to bring himself to tell Izuku that he won't be able to remain by his side when the time comes and thanks him instead.

End of Term Test Arc
Izuku and Katsuki are paired together and must fight All Might in their end of term test exercise. All Might tells the wonder duo to cooperate together and come at him to win.

All Might, Izuku, and Katsuki get onto a bus and drive to an uninhabited city where the test exercise will take place. All Might, Izuku, and Katsuki arrive in the city. All Might explains the test exercise: Izuku and Katsuki have two options of winning and passing the test exercise; they must either handcuff All Might or one of them must escape from the battlefield. Izuku and Katsuki have to accomplish either fighting to handcuff their opponent or one of them must escape the battlefield in 30 minutes. Izuku notes that this will test their flight or fight decision skills. All Might puts on super compact weighted bracelets to give himself a handicap. The test exercise begins. After a while passes, Izuku and Katsuki begin arguing. Suddenly, All Might throws a punch which devastates the area Izuku and Katsuki are in; All Might says that he will have to get involved.

Izuku is shocked at the level of All Might's (even though he knows that All Might is handicapped and severely weakened to begin with). All Might declares to the duo that he is a villain and collateral damage means nothing to him. All Might charges at the duo. Feeling All Might's pressure, Izuku tells Katsuki that they have no chance of winning and should run away. However, Katsuki refuses to run away. Katsuki uses Stun Grenade against All Might which distracts him. Katsuki charges at All Might, but the Symbol of Peace grabs Katsuki's face, stopping his advance. Katsuki launches a flurry of Explosions against All Might. However, Katsuki's Explosions do not even scratch All Might. All Might slams Katsuki down onto the ground. All Might turns his attention to Izuku who planned on running away. All Might questions Izuku on his decision to escape. Izuku recalls the Hero Killer and activates One For All Full Cowl, wondering why he suddenly recalled the Hero Killer. Izuku jumps into the air, but Katsuki has also jumped into the air; the duo collides into each other as a result.

All Might appears in the air with a guardrail in his hands; All Might slams the guardrail on Izuku which pins him down to the ground. Then, All Might punches Katsuki in the stomach, greatly injuring him and sending him flying backwards. All Might approaches Katsuki and says that he understands his jealousy of Izuku's sudden growth; All Might tells Katsuki that what he is currently doing is a waste and must grow his willingness to borrow other peoples' strength. The weakened Katsuki struggles to get up and tells All Might that if he must rely on other peoples' strength, then he would rather lose. Disappointed with Katsuki's decision, All Might prepares to finish off Katsuki; Katsuki tries to move but to no avail. Suddenly, Izuku activates One For All Full Cowl and breaks free of the guard rail; Izuku charges and punches Katsuki out of harms way.

All Might chases after Izuku and Katsuki. Suddenly, Katsuki appears from behind and attacks All Might with an Explosion which distracts All Might. However, one of Katsuki's Grenade Bracers is missing. Suddenly, Izuku appears behind All Might with Katsuki's missing Grenade Bracers equipped on him. Katsuki yells at Izuku to commence his attack; Izuku aims the Grenade Bracer at All Might and releases the grenade pin.

Izuku releases the grenade pin and blasts an immense Explosion at All Might at point blank range. After the Explosion is finished, Izuku and Katsuki dash towards the exit. All Might easily takes the Explosion, only coughing up a little blood. All Might is impressed with the duo's strategy; All Might notes that while their relationship will not improve immediately, Izuku and Katsuki's cooperation with each other in this practical test will be a great leap forward for them in the future. All Might decides to chase after the escaping Izuku and Katsuki, declaring that he will give it his all.

All Might catches up to Izuku and Katsuki and defeats them; All Might pins Katsuki down on the ground with his foot and dangles Izuku in the air with his arm. All Might praises Izuku and Katsuki for working together to try and defeat him but reminds them that working together is merely a per-requisite of the practical test.

Recovery Girl announces that Shoto and Momo are the first team to pass the exam. All Might is surprised to learn that his colleague, Shota, has been defeated. All Might smashes Katsuki into the ground with his foot. Katsuki finally understands that All Might is far too overpowered for him to stop and realizes that All Might is truly the strongest Hero and the world's most sky scrapping wall. Izuku tries activating One For All Full Cowl, but All Might stops him and throws him onto the ground. All Might decides to finish off Izuku and Katsuki.

Suddenly, Katsuki gets up and launches a big explosion against All Might, which distracts the Symbol of Peace. While All Might is distracted by the light, Katsuki grabs Izuku and throws Izuku towards the escape gate with an Explosion. To prevent Izuku from escaping, All Might uses New Hampshire and blasts himself into Izuku which crushes Izuku due to All Might's great weight and sends him tumbling down. Katsuki chases after All Might; Katsuki tells All Might that the Grenadier Bracers were to help him use his maximum Explosions without risk and admits that he was a fool for thinking that he could win without taking risks. Katsuki uses a huge Explosion against All Might (similar to the Explosion in the Sports Festival) and tells Izuku to escape; Izuku struggles to get up. Katsuki decides to sacrifice himself to hold off All Might so that Izuku has time to escape; Katsuki uses another huge Explosion against All Might. However, although the great Explosions have distracted All Might, the Symbol of Peace is still unscathed.

Izuku gets up and prepares to activate One For All Full Cowl so that he can leap towards the escape gate. Not allowing Izuku to make an escape, All Might prepares to attack Izuku but Katsuki intercepts All Might's attempt. Izuku successfully activates One For All Full Cowl and begins his escape while All Might smashes Katsuki into the ground. Izuku sees that Katsuki is in trouble. Despite being greatly injured, Katsuki yells at Izuku to escape and bites All Might's hand. All Might ignores Katsuki's desperate attempt and tells Izuku that he won't allow him to escape.

Surprisingly, Izuku does not rush towards the escape gate; instead, Izuku rushes back to help Katsuki. While rushing to help, Izuku remembers All Might's words; that when times are scary and uncertain, you face it all with a smile. Izuku smiles and punches All Might in the face. While All Might is suffering from slight recoil, Izuku grabs Katsuki who has fallen unconscious. Izuku rushes towards the escape gate with Katsuki in tow. All Might shrugs off Izuku's punch and watches him escape. All Might understands by now that Izuku is the type of person to save somebody; All Might notes that whenever Izuku tries to save somebody, there's never a wall in his way.

After Izuku and Katsuki pass the practical exam, All Might carries them to Recovery Girl's tent to be healed. Recovery Girls scolds All Might for not restraining himself during his battle with Izuku and Katsuki. Recovery Girl asks All Might to take Izuku and Katsuki back to U.A. to recover. After Izuku requests to stay, All Might leaves carrying an unconscious Katsuki in his arms, he notes that Izuku will be extraordinarily strong one day. All Might walks out of the tent and prepares to carry Katsuki back to U.A.. All Might notes that Katsuki himself is also incredible and that whenever there is a wall in front of Katsuki, he laughs at it.

School Trip Arc
After The Hero Incident involving Izuku occurs, Toshinori goes to the Police Station. Outside the Police Station, Toshinori greets Izuku and Naomasa; Toshinori apologizes to Izuku for not being there. Thinking about his conversation with Tomura, Izuku asks Toshinori if there were times when he failed to save someone. Toshinori tells Izuku that there were many times he could not save someone; Toshinori modestly admits that he is only human and cannot save everyone. Toshinori notes that his title, the Symbol of Peace, serves to inspire people and Heroes to play their roles so that more people can be saved. Izuku's mother arrives to pick Izuku up; Izuku comforts his crying mother, telling her that everything is fine. After Izuku and his mother leave, Naomasa theorizes that Tomura will probably target other students and decides that Hero schools must exercise more caution and become more proactive in implementing counter measures against villains. Naomasa advises Toshinori that leaving U.A. is also an option, but Toshinori decides against it. Naomasa concludes their conversation by saying that they will capture All For One this time, to which Toshinori agrees.

One day later after the League of Villains' Vanguard Action Squad capture Katsuki, Toshinori is in a meeting with the U.A. faculty. In the meeting, Toshinori is ashamed of himself for lounging around while his students were out fighting for their lives. Toshinori leaves the meeting when he gets a phone call from Naomasa, who informs him that they have located the League of Villains' hideout and requests his help in the rescue operation.

Hideout Raid Arc
The next day at night, Toshinori along with the Police Force and a large number of Pro Heroes await for their infiltration of the League of Villains' hideout. While waiting, Toshinori and Gran Torino converse to each other that All For One is making his move. The infiltration begins with the Police Force and the Pro Heroes standing outside the League of Villains' hideout; Toshinori prepares to attack.

Toshinori breaks into the hideout with Kamui Woods swinging in and restraining the League of Villains with his Lacquered Chains Prison while Gran Torino stops Dabi from using his Quirk with his kick. Toshinori checks Katsuki and compliments him for not being afraid, much to Katsuki's chagrin. After Kurogiri's attempt to bring the Nomus fail, Toshinori criticizes Tomura for underestimating them and declares that it is game over for him and his League of Villains.

However, Tomura refutes Toshinori's claim and orders Kurogiri to create portals so that they can escape, but Edgeshot knocks Kurogiri unconscious. Gran Torino asks Tomura the location of his boss, All For One. Tomura does not answer and instead screams out his hatred for Toshinori. Suddenly, mysterious black liquid appears out of thin air with Noumus appearing out of the phenomenon which surprises the League of Villains and the Pro Heroes; Edgeshot notices that the black liquid is not Kurogiri's doing since he is unconscious. More Nomus begin appearing from the masses of the mysterious black liquid. Toshinori grabs Katsuki. However, Katsuki begins dissolving into the black liquid and disappears, much to Toshinori's fury.

Tomura, Kurogiri, and the Vanguard Action Squad are entrapped in the mysterious black liquid. Toshinori and Gran Torino attempt to stop them but the mysterious black liquid teleports Tomura, Kurogiri, and the Vanguard Action Squad away from the hideout. Kamui Woods mulls over his failure in restraining the League of Villains while Edgeshot tells him not to worry since they could not do anything either. Four Nomus attack Toshinori, and he defeats them with Oklahoma Smash. Outside the hideout, Naomasa along with Enji and the Police Force continue battling the dozens of Noumus and have the upper hand. Toshinori appears and decides to leave the rest to Enji.

Toshinori manages to find Sensei and attacks him, but Sensei blocks the attack. Toshinori declares that he will take everything back while Sensei wonders if the Symbol of Peace will attempt to kill him again.

All Might and Sensei clash, which creates a shockwave that sends Katsuki, Tomura and the Vanguard Action Squad backwards. Both Sensei and All Might criticize each other for becoming weaker. All Might declares that he will save Katsuki and won’t repeat the same mistake as he did five years ago and this time he will definitely put Sensei behind bars along with the League of Villains. All Might charges at Sensei. However, Sensei sends a huge blast wave at All Might, causing the Symbol of Peace to be sent flying away at great force. Sensei’s blast wave attack not only hits All Might but destroys several buildings in the process.

Despite being sent several miles away, All Might quickly recuperates and returns to the battlefield by jumping to it, refusing to allow Sensei to escape and charges at him. All Might and Sensei clash once again. Meanwhile, Katsuki is fending off some of the Vanguard Action Squad; All Might attempts to help Katsuki only for Sensei to intervene and stop him. Suddenly, Izuku, Eijirou and Tenya appear above in the air; Sensei sees the trio and attempts to attack them, but All Might intervenes by punching Sensei.

All Might is surprised with Izuku and the other students' presence. Gran Torino appears at the battlefield, knocking out Spinner, Kenji, Mr. Compress and is annoyed that Izuku has taken on All Might’s characteristics, while All Might himself is still surprised that Izuku and some of his fellow students came to rescue Katsuki. However, All Might is pleased with their intervention as he can now fight Sensei without holding back.

After Izuku and his friends flee with Katsuki and Tomura along with the Vanguard Action Squad are teleported away, All Might charges at Sensei, but Sensei uses his Transmission Quirk to teleport Gran Torino in front of him, using the elderly Hero as a human shield which causes Gran Torino to take All Might’s attack instead. Sensei expresses his hatred for All Might as he is the one who brought down his comrades in the past and while he descended into darkness, All Might rose to the top as the Symbol of Peace. Sensei prepares to fire his blast wave move, intending of blowing away Gran Torino and All Might at the same time. However, All Might pulls Gran Torino away and uses Detroit Smash to cancel out Sensei’s blast wave move.

Sensei sees that his destruction of the city has brought chaos and decides to put the innocent civilians in danger so that All Might won’t be able to fight at full strength. Furious with Sensei’s sadism, All Might grabs his arm while throwing Gran Torino away for safety. All Might admonishes Sensei for all the despicable crimes he has committed and for his misanthropy.

All Might punches Sensei in the face, shattering his mask; however, All Might’s punch wasn’t strong enough to finish off Sensei. As Gran Torino calls out to him, All Might turns back into his true form. Sensei says that All Might would not be the first to criticize him as he has heard those same lines before, from the previous One For All successor: Nana Shimura.

All Might whose face has partially reverted to its true form is angry at Sensei for mentioning his predecessor’s name, Nana Shimura. Sensei notes that Nana Shimura was all bark and no bite, only going on about her ideals and was not even strong; Sensei mocks Nana for her uselessness and mentions that she died an embarrassing, shameful death. Furious, All Might prepares to attack Sensei. However, Sensei uses his blast wave technique against All Might, causing the Symbol of Peace to be blasted into the air. Gran Torino catches All Might and lands him to safety on the ground. Gran Torino advises All Might to not listen to Sensei’s provocations and that due to Sensei’s different Quirk usage and strategies; he should only attack when Sensei lets his guard down.

Up in the sky, news helicopters are broadcasting the battle. Sensei decides to sever the trust in Heroes once and for all. Sensei once again expresses his hatred for All Might due to taking something away from him and wants him to die in the most gruesome way possible. Sensei fires another blast wave attack at All Might. All Might, seeing that an innocent civilian is trapped under rubble behind him, blocks Sensei’s blast wave attack which saves the civilian from being harmed. However, All Might who blocked the blast wave attack has caused him to expend his power and he reverts to his true form. Sensei relishes in the fact that All Might’s true form has been exposed for all to see.

Everyone around the country sees All Might’s true form and begins panicking. Sensei mocks All Might for the pitiful state he is in. However, All Might doesn’t care about his rotting body nor his exposure to the world; All Might declares that his spirit burns strongly which is what truly matters. Wanting to break his spirit, Sensei reveals that Tomura Shigaraki is Nana Shimura’s grandson, which demoralizes All Might. All Might refuses to believe, but Sensei tells the Symbol of Peace that it is the truth. Sensei wonders why All Might isn’t smiling and sarcastically remarks about All Might’s smile, which is something Nana would always do. All Might’s spirit is greatly demoralized by Sensei’s sarcasm while Sensei continues relishing in All Might’s pitiful state. However before he could fall in complete despair, the innocent civilian under the rubble encourages All Might to win and help her.

Around the country, the people who are watching refuse to believe that All Might will lose even though he isn’t at his best and do not care about his true form since he has attained victory one way or another. Many citizens who are watching rally behind All Might and encourage him to win. In response to this, Izuku and Katsuki also encourage All Might shouting at him to win. Invigorated by the civilian pleas, All Might regains hope as he activates One For All throughout the right side of his body, transforming it back into its Hero form. All Might smiles and states that Heroes have many things to protect which is why they don’t lose.

All Might activates One For All throughout the right side of his body. Endeavor, Edge Shot and Kamui Woods arrive; Endeavor and Edgeshot fight All For One with the former flabbergasted with All Might's appearance. Kamui Woods rescues Best Jeanist, Mount Lady and Gang Orca while Tiger rescues the trapped civilian; Tiger encourages All Might to win since he is everyone's Number One Hero.

Growing tired with the sentimental talk, All For One blasts Endeavor and Edge Shot back. All For One activates a numerable amount of his strongest Quirks in his right arm, causing it to become an enlarged mutated arm filled with numerous deadly screws and hardened minerals.

All For One charges at All Might with his heavily empowered and mutated arm. While heading towards All Might, All For One knows from battling him that All Might no longer has One For All and tells All Might that the person who was given One For All by him is Izuku Midoriya. All For One taunts All Might by saying that he has also failed as a teacher towards Izuku due to his apprentice's recklessness. Both All For One and All Might clash by punching each other with their enhanced fists, which creates a huge shockwave that devastates a great portion of the city. As they struggle, All For One uses his impact Recoil Quirk to revert all the damage to All Might. However, All Might transfers One For All to his other arm, sacrificing his right arm but renders Impact Recoil ineffective. All Might says that he must indeed criticize Izuku for his actions. All For One is shocked that All Might would go to such lengths to protect his leftovers of One For All and admits that he miscalculated. All Might refuses to die until he has finished bringing up Izuku, he then counters by throwing his empowered left arm and punch at All For One who has left his guard open.

All Might has punched All For One, successfully hitting him. However, the punch All Might delivered was meant to lower All For One's guard which worked. All Might transfers One For All to his right arm and prepares for his final attack he will ever use. All Might uses United States of Smash on All For One, which creates a great shockwave. After the dust clears, All For One is in a crater, badly beaten and unconscious.

All Might raises his arm to signify his victory; the reporter from the news helicopter announces All Might's victory. All Might transforms into his Hero form while raising his arm, signifying that he is the Symbol of Peace which causes the citizens watching to start celebrating; Edge Shot wants All Might to preserve his strength, but Gran Torino stops him as he wants All Might to enact his dream of being the Symbol of Peace for one last time.

With the battle over, Pro Heroes begin carrying out rescue operations to save people who are trapped under rubble as a result of All Might and All For One's battle. Meanwhile, Endeavor and All Might watch All For One being placed in the iron maiden. Now that All For One is properly imprisoned, All Might points to the camera and delivers a message "you're next". The citizens watching take All Might's message as a warning to all villains out there, causing the citizens to praise All Might and start celebrating again. However, Izuku knows what All Might's message truly meant; that his time as Symbol of Peace has come to an end and he (Izuku) is the next successor. Izuku now realizes that All Might's time has truly come to an end and starts crying.

At a hospital, All Might who is bandaged and recovering states that he can no longer use One For All and that although he can no longer be the Symbol of Peace, he still has things to do. Naomasa is in disbelief that Tomura Shigaraki is Nana Shimura’s grandson. On that topic, Gran Torino comments that Nana Shimura and her husband had a child. However, after her husband died due to heroics, Nana sent her son to a foster family so that he can stay away from the world of heroics. Nana then informed Gran Torino and Toshinori to not get involved with her son. All Might wishes to find Tomura, however, Gran Torino tells All Might that he is in no position to help Tomura since he has would not be able to see Tomura as a villain. Gran Torino and Naomasa decide that they will handle the search for Tomura. Gran Torino suggests to All Might that he must remain at U.A and carry out what he must still do; helping his successor, Izuku Midoriya.

All Might meets Izuku at the Dagobah Municipal Beach Park. All Might greets Izuku with a Texas Smash as a part of his scolding. All Might reveals to Izuku that he can no longer use One For All and demonstrates this by entering his Hero form, only to exit it in a split second afterwards. All Might informs Izuku that he is retiring as a Hero since he is in a state where he cannot fight anymore. All Might scolds Izuku for never doing what he is told and for his recklessness in rescuing Katsuki. However, All Might is glad that his recklessness did not get him injured this time and is proud of Izuku for that. All Might hugs Izuku and apologizes for not being a proper mentor towards him, but from now on he will focus solely on Izuku’s development and training. Izuku begins to cry, to which All Might scolds him for again.

All Might returns to U.A where Mr. Principal thanks him for saving the day. Mr. Principal announces a plan he would like to implement; transitioning U,A to a boarding school as a means to mitigate the safety issues and asks for Shota's cooperation.

Shota and All Might visit the homes of Class 1-A. He and All Might visit Kyoka's home, where Kyoka's father is not to happy with U.A's safety measures and has doubts in U.A's ability to protect her if she were to relocate to U.A's dormitories; Shota acknowledges that U.A has been negligent in its duty to safeguard its students and vows to correct this safety issue as well as promising to make Kyoka into a fine Hero. Kyoka tells Shota to relax as her father has already agreed to allow her to relocate to U.A's dormitories.

Shota and All Might visit Katsuki's home, where Katsuki's mother is more than happy so allow her son to relocate to U.A's dormitories. Katsuki's mother is confident in U.A because Shota sees her son for who he is instead of what he can do. Katsuki's mother also reasons that her son, even though she was worried, returned home safe and sound from his captors thanks to the Pro Heroes which is why she is confident in U.A's ability to safeguard and raise her son. As Shota and All Might leave the Bakugo household, Katsuki asks All Might what Izuku is to him. Unable to tell Katsuki the truth, All Might informs him that Izuku is a student to him who has great potential just like Katsuki. Satisfied to a degree with All Might’s answer, Katsuki thanks All Might for everything and goes back inside his house. Shouta decides to visit the other Class 1-A families by himself while All Might goes to visit Izuku.

All Might decides to visit Izuku’s home by himself while Shota visits the rest of Class 1-A. All Might enters the Midoriya household, with Izuku and his mother flabbergasted that the Number One Hero has entered their abode. After the three sit down at the table, All Might asks Izuku’s mother for her permission to send Izuku to the U.A dorms. However, Inko is against it. Inko explains that she is worried about her son since his Quirk damages him rather than helps him and is deeply concerned about her son’s future as a Pro Hero after witnessing All Might’s brutal battle, unable to bear the fact that Izuku will also have to face such bloody battles with no hope possibility of full recovery. Inko states that she has no confidence in U.A and is unable to entrust her son to them.

Izuku tries to convince his mother that his injuries are a result of his inability to control his Quirk, but Inko replies that regardless it is still the responsibility of U.A to take care of their students which they have not done. Inko understands that she is being a strict parent but the safety of her child is her number one priority and she is fine with Izuku continuing to become a Hero since it is his dream as long as he is in a safe environment, which is why she wants to send Izuku to another school. Although he understands his mother, Izuku wants to continue his dream at U.A. since that is where All Might became a hero.

Izuku runs out of the room while All Might understands Izuku’s frustration; that it must be painful to not being able to study at the same place his idol went to. Izuku returns to the room with a letter in his hand; the letter is a thank you from Kota. Izuku tells his mother that at the training camp, he saved a boy who hated Quirk and Heroes from a villain. Izuku understands that he has a long way to go but for a little while, Kota and his thank you letter made him a hero. Izuku declares that even if he cannot study at U.A, he will still keep dreaming to become a hero.

All Might is shocked that Izuku is willing to continue his dream even though it is not as the same place as his idol; All Might is impressed with Izuku’s growth and is glad that he is going on his own path instead of following him, his idol. All Might transforms into his Hero form and kneels before Izuku and Inko, bowing his head, much to their shock.

All Might apologizes to Inko for his negligence as Izuku’s teacher and understands that she is worried about the bloody path of a Hero; All Might asks Inko to allow him to walk together with Izuku down his path so that he doesn’t have a bloody future. The former Symbol of Peace also understands Inko’s concerns about the current U.A and tells her that they are reforming their ways. All Might promises that he will nurture and protect Izuku even at the cost of his own life.

Inko is shocked at All Might’s resolve, causing her to fall to her knees. Inko states that all she wants is Izuku to be happy and tells All Might that he should never trade his life away for someone else’s sake. Inko tells All Might to continue living and that as long as he can protect and nurture Izuku, she will reconsider her decision to not send Izuku to live at U.A. All Might pledges to protect and nurture Izuku while Izuku tells his mother that he will not worry her.

Outside, All Might compliments Izuku’s mother, telling Izuku that she reminds him of his master. All Might leaves and tells Izuku that he will see him at U.A.

Hero License Exam Arc
All Might along with Cementoss, Midnight and Ectoplasm were the repossessed by training class A and B students to develop their Quirks and special techniques before the provisional hero license test.