Vs. Hero Killer Arc

The Field Training Arc is the sixth story arc in Boku no Hero Academia and the sixth story arc in the Yuuei Beginnings Saga.

Izuku, along with his classmates, travel to their chosen workplaces to gain Hero experience and training under the supervision of Pro Heroes. Meanwhile, evil begins moving about in Hosu, eventually leading to a confrontation between three young Heroes and their first formidable villain.

A Meeting for Trying Out New Names
Two days after the Sports Festival, Izuku is on a train to Yuuei. While on the train, some of the passengers recognize him from the Sports Festival, acknowledging his prowess. At Yuuei, Tenya is running and passes by Izuku, telling him that they should be at least 10 minutes earlier for school. After arriving inside, Tenya tells Izuku that he doesn't have to be worried about his older brother as he will be fine and apologizes for causing him unnecessary concern.

In their class, the students of Class 1-A are discussing the attention they received from the Sports Festival. Class 1-A's homeroom teacher, Shouta, enters, causing everyone to hurry back to their seats. Shouta has fully recovered from his injuries, no longer needing to wear bandages. Shouta tells his students that their Hero Informatics Period will be about formulating their Hero names, much to their excitement. Shouta says that the formulation of their potential Hero names are due to the nominations by Pro Heroes. He says that the nominations from the Pro Heroes this year are more akin to expressions of interest in their potential futures. Shouta shows his class their tally of nominations, saying that the tally of nominations are usually more balanced but this year the attention points to Katsuki and Shouto. Shouta says that regardless of whether or not they received nominations he will be having them go get work-place experience. Shouta says that they did get first hand experience at the USJ unfortunately but he thinks that experiencing the activities of Pro Heroes first hand will prove to be more fruitful training. Soon, Midnight arrives to which Shouta explains to his class that he requested Midnight to evaluate their Hero names. Shouta tells his class that the way their futures end up will depend on the image projected by the Hero names they choose.

Midnight gives Class 1-A 15 minutes to decide on Hero names. After 15 minutes have past, each student starts to reveal the Hero name they chose.

After most of the Class 1-A have revealed their Hero names, only Izuku and Tenya are left (besides Katsuki who needs to change his name). Tenya has struggled in deciding whether to use his older brother's Hero name Ingenium or not (after Tensei asked Tenya to take up the torch due to his legs being completely crippled and thus cannot continue being a Hero). Eventually, Tenya is unable to bring himself to use Tensei's Hero name and instead uses his own name as his Hero name.

Izuku is the last student yet to reveal his Hero name. Izuku reveals his Hero name, causing some of his classmates to comment if he is okay with it, to which Izuku replies that up until now he didn't like it at all. Izuku says, however, that someone came along and changed the meaning of the name making him happy. Izuku reveals his Hero name to be Deku, saying with confidence that Deku will be his Hero name. Katsuki looks on in anger while Ochako smiles at Izuku's Hero name.

In Yuuei's Faculty room. Cementoss 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. Back in Class 1-A, Katsuki changes his Hero name to Baron of Explodo-Kills but Midnight comments that the name won't do.

Choices for Workplace Training: Gran Torino Enters the Fray!
After Class 1-A has finished formulating their Hero names, Shouta tells his students that their field training will be one week long. He says that the students who received nominations will get a personalized list of work places to choose from. Shouta gives the students who didn't receive nominations lists that have 40 work places to choose from. Shouta tells his class to choose one work place from their respective lists, saying that they have until the end of the week to make their work place choices.

After school that day, All Might appears in front of Izuku Midoriya 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 Yuuei 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. Izuku notes that even All Might is nervous from talking about Gran Torino, wondering how scary the retired Pro Hero was. 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 go see what he can learn from him. Before leaving, All Might informs Izuku that his Hero costume has been repaired. Thus, Izuku chooses Gran Torino as his work place to train at.

At the same time in the staff room, Shouta is surprised that some of his students chose the work place that they want to train at already. He looks at Tenya Iida's work place choice which is the Hosu City Hero Office, noting that there were better nominations for him to choose from. The day of the work place field training arrives. Shouta Aizawa is at the station with his class to escort them to their work places safely. Shouta tells his students that while they do have their Hero costumes with them he reminds them not to wear them in public and not to lose them. Shouta tells them to have manners and wishes them luck. As Tenya walks to his train, Izuku tells Tenya that if he needs someone to talk to he can talk to him and Ochako (with her nodding in agreement) as they are his friends. Tenya replies that he will. However, as he walks away, Tenya is shown with a scowl on his face.

After his train stops, Izuku arrives near the work place destination and walks to Gran Torino's home address. Izuku arrives at a dilapidated building. Izuku enters and tries introducing himself but was horrified to find the elderly retired Pro Hero on the floor seemingly dead with blood-like liquid splatter below him. Gran Torino suddenly gets up, shocking Izuku in the process, then he began explaining that he was carrying a plate of sausages with ketchup on them, but fell and got ketchup everywhere. Gran Torino asks the boy his name to which Izuku tells him his name and that he is from Yuuei. However, Gran Torino does not recall nominating him. He suddenly remembers, calling Izuku "Toshinori" in the process, much to Izuku's annoyance. Izuku tries to leave the apartment to speak to All Might on his phone, but Gran Torino asks Izuku to fight him with One For All, saying that he wants to see how well Izuku can handle One For All, wanting him to put his Hero costume on and fight him. Gran Torino once again forgets who Izuku is. Thinking that Gran Torino is playing games with him, Izuku declares to the elderly Hero that he needs to learn how to control his power as soon as possible since All Might is running out of time, telling the elderly Hero that he doesn't have time to be fooling around. Izuku starts leaving, visibly disappointed. Suddenly, Gran Torino jumps and leaps in front of Izuku at an incredible speed, stopping Izuku from leaving. Gran Torino tells Izuku that since Izuku has a goal to learn how to control his power, then he has all the more reason to stay. The elderly Hero asks Izuku to use One For All and fight him.

The Mystery of Noumu Unraveled
At Yuuei, Naomasa meets with All Might. He tells All Might that the Police Force have tried everything to get information out Noumu, however, everything they tried did not work. Naomasa says that they instead looked into Noumu'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 Noumu 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 Noumu'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 Noumu acquired the Quirks through advanced genetic familial permeation). Naomasa theorizes that someone with a Quirk that can grant Quirks is behind Noumu's acquisition of multiple Quirks. All Might becomes concerned.

The Training Begins
In Gran Torino's apartment, Izuku puts on his Hero costume (which has not only being repaired but redesigned as well) and faces Gran Torino in a mock battle. However, Izuku is unable to keep up with Gran Torino's incredible jumping speed and is constantly hit. Izuku prepares to use One For All and predicts that Gran Torino will attack him from behind. Izuku's prediction turns out to be correct, allowing Izuku to get into position to hit Gran Torino, but Gran Torino pushes Izuku's arm out of the way. The mock battle ends with Gran Torino telling Izuku that he is too rigid and his awareness is disjointed which are some reasons he is unable to use One For All properly. Gran Torino explains that Izuku's main problem is that thinks One For All is special. Izuku asks Gran Torino to explain what he means, but the elderly Hero tells Izuku to figure that out for himself and goes to eat something.

In the borough of Hosu City, Tenya in his Hero costume goes on patrol with one of the Pro Heroes from the Hosu City Hero Office. Tenya ponders that the Hero Killer Stain was the one who critically injured his older brother Ingenium, deciding that he himself will chase after Stain, unable to forgive the Hero Killer for his crime, declaring that he will avenge his older brother.

Meanwhile, in the Villain Alliance's hideout, Kurogiri brings Stain to the Villain Alliance hideout to meet with Tomura Shigaraki. Stain sees that it was Tomura's Villain Alliance that raided Yuuei and that Tomura wants Stain to join his Villain Alliance. Stain asks what Tomura's goal is, to which Tomura replies that he wants to murder All Might and destroy anything that is unsatisfiable to them such as some of the students from Class 1-A. Seeing that Tomura is being childish, Stain says that Tomura is being foolish and that there is no sense in bloodshed without a cause. The mysterious voice on the monitor orders Kurogiri to allow Stain and Tomura to continue talking, saying that Tomura's meeting with Stain (an experienced infamous villain) will stimulate Tomura's growth.

Back in Gran Torino's apartment, Izuku ponders deeply about his problem with controlling One For All that Gran Torino pointed out. Izuku suddenly figures out what Gran Torino meant; that he has been thinking of One For All as a trump card which has made him "rigid" in its use (unable to use it properly) and that in order to control One For All properly he must be "flexible" (thinking of One For All as a simple body function). Izuku goes to write this crucial discovery down in his notebook, dumbfounded that he didn't realize the problem sooner when it was in front of him all the time. Izuku decides to drill in the repetition of thinking One For All flatly (as a simple body function). Gran Torino is outside and overhears Izuku finding the solution to his problem in controlling One For All. Gran Torino ponders that Izuku's thought process is flexible and commends All Might for finding an excellent successor.

Katsuki arrives at his workplace of choice, which is revealed to be Best Jeanist's hero office, located in the Tokyo metropolitan area. In the office, Best Jeanist tells Katsuki that reforming brutish people is his job and that he will show Katsuki what is it that makes people Heroes.

Eijirou's workplace of choice is revealed to be Force Kind's hero office. As Force Kind explains the mechanisms of his salary, Eijirou and Tetsutetsu are surprised to see each other in the same workplace and greet each other with handshakes. Force Kind tells Eijirou and Tetsutetsu that he will explain their practical operations.

Ochako is at Gunhead's hero office which is her workplace of choice. Ochako listens to Gunhead's explanation about what his office does and how he earns income.

Momo and Itsuka have both chosen Snake Hero Uwabami's workplace to get experience at. Uwabami explains to the duo about her Hero office's work and how to earn popularity. Uwabami tells Momo and Itsuka that she has a commercial to film and tells the duo to get to know each other. Itsuka is somewhat disappointed about not getting the opportunity to experience Pro Heroes at work but Momo is optimistic about getting to study under the Snake Hero, causing Itsuka to comment on her upbeat attitude.

Quirk Problems: Izuku's New Quirk Control
It is night time on the first day. At Gran Torino's apartment, Izuku sneaks out and goes to an alley in order to test out his new discovery about One For All (thinking of One For All as a simple body function). In the alley, Izuku tries out his new method only to fail. Izuku continues this self training until morning.

In the morning, Izuku tells Gran Torino that he was trying his new method but found it to be difficult. Gran Torino comments that it is difficult due to him only just discovering the proper method of using One For All and states that All Might was able to use One For All normally when he first obtained it thanks to his body which is why All Might’s guidance towards Izuku isn’t working. Gran Torino informs Izuku that All Might couldn’t handle One For All emotionally due to it being passed down by a late friend. Izuku is fascinated by All Might’s past and asks about All Might’s predecessor, much to Gran Torino’s surprise. A delivery arrives at the door which Izuku fetches. The delivery is a new microwave to replace the other one Gran Torino broke yesterday during their mock battle. Gran Torino decides they should have breakfast now, telling Izuku to set up the new microwave.

Izuku sets up the new microwave and warms up the breakfast which is taiyaki. Izuku serves Gran Torino his taiyaki. Gran Torino excitedly takes a bite but the taiyaki turns out to be mostly frozen. Annoyed, he goes to check the microwave, telling Izuku that he didn't put the microwave's plate in properly and as a result it didn't turn and only a part of the taiyaki was heated. His comment causes Izuku to realize his next problem with One For All; that he has been using One For All on one body part and not on his whole body. Izuku activates One For All throughout his entire body with Gran Torino being impressed with Izuku's quick learning. He asks if Izuku can move while using One For All throughout his body, to which Izuku replies that he is not sure. Gran Torino asks if he can test whether Izuku can move around while using One For All throughout his body, and Izuku replies that he can test him.

Gran Torino tells Izuku that if he can move around while having One For All coursing through his body, then he will be drawing a clear line from how he was during the Sports Festival. Gran Torino says that their mock battle will be three minutes for starters. The mock battle begins and Gran Torino hits Izuku from behind, stopping the flow of One For All throughout Izuku's body. Gran Torino attacks Izuku from all directions while Izuku stands helplessly unable to counter. After falling to the ground, Izuku realizes that Gran Torino's speed is too fast for him to counter and decides to regroup. Izuku crawls under the couch and activates One For All throughout his body again. Gran Torino heads towards the couch, but suddenly, Izuku punches the couch away, sending it flying and stopping Gran Torino's attack.

Now that One For All is flowing throughout his body, Izuku leaps into the air and nearly manages to hit Gran Torino, however, the elderly Hero manages to dodge in the nick of time. Gran Torino jumps forward and prepares to attack Izuku from behind, but Izuku dodges the elderly Hero's attempt by jumping into the air above him. Izuku, seeing that he is in a perfect position, sends a One For All enhanced punch at Gran Torino. However, the elderly Hero manages to dodge Izuku's attempt. Izuku starts falling down while Gran Torino leaps from the wall and strikes Izuku in his stomach, smacking Izuku down onto the ground and causing One For All to stop its flow.

Gran Torino sees that three minutes are up and ends the mock battle for now. Izuku laments on his lack of ability to keep the activation of One For All throughout his body properly. However, Gran Torino compliments Izuku's intelligence. The elderly Hero notes to himself that Izuku has dramatically changed in such a short space of time and compliments Izuku for being able to graze him (a cut is shown on Gran Torino's face) even though he was using his own power earnestly. Gran Torino states Izuku that he must get used to using One For throughout his body and informs him that they will continue training after breakfast. After breakfast, Izuku continues his training with Gran Torino.

Tomura's Hidden Evil: Stain's Plan
At the Villain Alliance hideout, Stain's meeting with Tomura turns into a fight. Stain overpowers Tomura with ease and pins Tomura down onto the ground, stabbing Tomura's right shoulder with one of his daggers while pointing the other dagger at Tomura's neck. Stain tells the pinned down Tomura that creeds and convictions are need to accomplish anything and without them the amateur villain will not survive. Tomura desperately asks Kurogiri to send Stain away, but Kurogiri is unable to move at all presumably due to Stain's Quirk. Stain states his hatred for the current society; believing it to be overrun by fake Heroes and Villains who throw their power around timelessly. Stain prepares to cut Tomura's neck with his dagger as well as the hand on his face, but Tomura grabs the dagger with his hand and begins disintegrating it. Tomura tells Stain that while he doesn't have such serious creeds, he does have a desire; which is to crush the society where All Might is set up in, wanting to plunge it into the ground. Tomura completely disintegrates Stain's dagger. Stain leaps backward away from Tomura. Stain concludes that while their goals are different, his and Tomura's desire to destroy the current society is one thing they have in common. Stain tells Tomura that he has tested his mettle and concludes that he has a crooked creed dwelling within him and wonders what that creed will sprout. Stain declares that he might spare the Villain Alliance and won't dispose of it once he has ascertained them with his own eyes. Seeing that his business with the Villain Alliance is over, Stain demands to be returned to Hosu as he has unfinished business there.

In the Hosu Hero Office, Tenya has arrived back from patrolling. Tenya has gathered information on the Hero Killer Stain, the villain who severely injured his older brother and realizes that Stain has an attack pattern. Tenya concludes that Stain will without a doubt be in Hosu to attack three more Pro Heroes. Tenya, in a silent rage, tells Stain to appear so that he himself can dispose of Stain with his own hands.

Chaos and Destruction Erupts in Hosu
It is the third day of workplace training. It is 5:00 PM and Izuku is on the floor injured due to his training, having been training since the first day. Gran Torino decides to end Izuku's training in One For All for now, not wanting Izuku to become stale due to fighting him all the time. Izuku protests but Gran Torino denies Izuku's request to continue training in One For All. Gran Torino declares that they will move on to phase two which is workplace experience. Izuku cleans himself up and puts on his Hero costume. Izuku and Gran Torino leave the apartment. Gran Torino tells Izuku that fighting him all the time will make him stale and now wants Izuku to experience fighting in all types and kinds of situations. Gran Torino tells Izuku that they will be going on an excursion and calls for a taxi. In the taxi, Gran Torino explains that highly populated areas are where crime is rife, causing Izuku to ask if they will be taking a train to Shinjuku to which Gran Torino says they will. Izuku realizes that they will be passing Hosu along they way and begins thinking about Tenya, worried about him and decides to contact him later. The taxi takes Izuku and Gran Torino to the train station where they board a train that will take them to Shinjuku.

In Hosu, Tenya is out patrolling again with Normal Hero. He asks Tenya if he is chasing after the Hero Killer Stain, thinking that would be the only reason Tenya came to the Hosu Hero Office. Normal Hero tells Tenya not to act out on a personal grudge. He apologizes for his question to which Tenya replies that he appreciates his warning. However, Tenya ponders that if he doesn't get revenge, what should he do with his rage and emotions, clenching his hand into a fist in anger.

Kurogiri warps himself, Stain and Tomura to Hosu. Tomura notes that Hosu is quite prosperous while Stain says his goal is to reform Hosu by sacrificing the "fake" Pro Heroes that work there. Stain states his belief; that the title of Hero should only be bestowed onto people who achieve great undertakings, saying that there are too many "fake" Heroes that only work for money. Stain leaves to finish his business, saying that he will keep appearing until society realizes its error and jumps off the building. After Stain leaves, Tomura complains about Stain's constant preaching, to which Kurogiri tells Tomura that he shouldn't mock Stain for his preaching, stating to Tomura that Stain's villainous methods have produced great results which intrigues Tomura. Tomura concludes that he and Stain will never get along which irritates him. Wanting to relieve his anger through destruction, Tomura orders Kurogiri to release the Noumus. Kurogiri warps three Noumus to their location and Tomura orders the Noumus to attack Hosu.

The train that Izuku and Gran Torino are on passes Hosu. On the train, Izuku tells Gran Torino that they will arrive at night, to which Gran Torino replies that they will, explaining that many villains appear at night and thus they will be able to get experience more easily. Izuku takes out his smartphone and sees that Tenya has read his message but did not reply. Suddenly, the train experiences an emergency stop and a Pro Hero comes crashing into the train, much to Izuku's and Gran Torino's shock. Immediately afterwards, a creature that looks similar to Noumu appears. Izuku tries to take action, but Gran Torino orders Izuku to stay put. Gran Torino jumps from his seat and slams himself into the Noumu-like creature, smashing the Noumu-like creature and himself out of the train and into the air above Hosu. Izuku tries to check on Gran Torino's safety but sees that Hosu is ablaze, shocked at what is transpiring and starts worrying for Tenya's safety.

Tenya vs Stain: Pro Heroes vs The Three Noumus
Stain is in an alley, overhearing the chaos in Hosu and realizes that Tomura has made his move. Stain decides to leave Tomura to his own mechanisms while he finishes his business, preparing to kill a Pro Hero with his katana. However, Stain feels the presence of someone approaching him from behind and uses his katana to slash at the person, knocking the person down to the ground as well as knocking off the person's helmet and glasses (which is revealed to be Tenya). Stain sees that the person who tried to attack him is a child, telling the child to leave. Tenya gets up, telling Stain that he has been searching for him and looks at the Hero Killer with vengeful eyes. Stain points his katana at Tenya and says that he has avenging eyes, warning Tenya to not meddle with him and that if the situation demands it children will also be targets. Stain prepares to go and finish his job of killing the Pro Hero. Seething with rage, the angered Tenya yells to Stain that he is the brother of a Pro Hero he cut down and he has come to stop Stain in his stead. Tenya tells Stain to never forget his Hero name; Ingenium, which is the name of the Hero that will take him down. Seeing that Tenya is serious about being a Hero, Stain tells Tenya to prepare for death.

Izuku exits the train and starts running towards Hosu to help Gran Torino against the Noumu-like creature.

Gran Torino had smashed the Noumu-like creature into a small building. The Noumu-like creature slashes at Gran Torino but the elderly Hero jumps out of the way in time, dodging its attack. Gran Torino sees that the Noumu-like creature is about to attack two civilians. Gran Torino jumps at the Noumu-like creature in order to save the civilians. However, the Noumu-like creature is scorched by flames, forcing Gran Torino to stop his attack and back away. Endeavor, the Hero who scorched the creature, says that he hasn't made acquaintances with the elderly Hero, telling Gran Torino that he will deal with the Noumu-like creature.

Izuku has arrived in Hosu and witnesses a battle between the Pro Heroes and two Noumu-like creatures. Izuku is surprised that Tenya isn't at the battle and starts pondering. Izuku quickly figures out that Tenya came to Hosu to find and hunt down the Hero Killer Stain. Izuku leaves the battlefield and searches for Tenya.

On top of a building, Tomura praises the three Noumus for their destruction. Kurogiri asks Tomura if he will join the attack, however, Tomura replies that he won't because he is injured. Tomura says that when dawn breaks the world will forget about Stain.

The battle between Stain and Tenya begins. Tenya uses a high speed kick, only to be dodged by the Hero Killer. Stain smashes Tenya into the ground and stabs Tenya's shoulder with his katana. Stain says that both Tenya and Tensei lost because they are fake Heroes, causing Tenya to rebuke the Hero Killer's claim, declaring that Tensei was a true Hero and that he will kill Stain to avenge him. Stain advises Tenya to first save the injured Pro Hero, which shocks Tenya. Stain says that he must not act out of vengeance since that is the act furthest from the title "Hero". Stain licks his bloodied katana and activates his Quirk which immobilizes Tenya. Stain is about to deliver the finishing blow. However, Izuku suddenly appears, having activated One For All throughout his body and punches Stain in the face with his enhanced might, preventing the Hero Killer from finishing off Tenya. Izuku announces his arrival and declares that he came to save Tenya.

Izuku Arrives!: An Unexpected Ally Comes To The Rescue
Izuku asks Tenya if he can move, but Tenya tells Izuku that he is immobilized. Stain praises Izuku for his efforts and threatens Izuku that he will kill Tenya if he gets in the way, asking the young Hero what he will do. Izuku plans on what to do; two people are injured and require protection. Izuku decides that he must protect Tenya and the Pro Hero by trying to drive Stain away. Tenya orders Izuku not to get involved since his fight with Stain has nothing to do with him. Izuku responds to Tenya's order, saying that Heroes would not be able to do anything by following Tenya's logic. Izuku puts on a brave face and says that getting involved in other people's business is one of the principal qualities of a Hero; Stain smiles at Izuku's statement.

Izuku and Stain begin their battle; Izuku activates One for All Full Cowl throughout his body and Stain charges at the young Hero. Izuku manages to get close to Stain and runs through the gap between Stain's legs, avoiding the Hero Killer's katana and dagger slash. Stain counters by slashing at Izuku with his katana, but Izuku dodges by jumping into the air and above him. Izuku, above the Hero Killer, uses 5% Detroit Smash on Stain, delivering a powerful blow to Stain's head. Tenya is shocked at Izuku's fast movements, comparing them to Katsuki's movements. Stain, unfazed by Izuku's move, licks his dagger and activates his Quirk; Izuku becomes immobilized and unable to move. Izuku wonders why Stain's Quirk is working as he never managed to cut Stain. Izuku realizes that it is blood that allows Stain to activate his Quirk.

Stain, impressed with Izuku's actions, decides to spare Izuku, saying that there is worth in keeping him alive Stain prepares to kill both Tenya and the Pro Hero since they according to him have no worth. Izuku yells at Stain to stop but to no avail. Suddenly, a column of fire and a column of ice attack Stain, but Stain manages to avoid the attack of fire and ice in the nick of time. Shouto reveals himself, being the one that attacked Stain with fire and ice. While Izuku and Tenya are surprised at Shouto's arrival, Shouto tells Izuku that Izuku didn't texted the message specific enough and caused him to arrive almost late.

Shouto begins battling the Hero Killer and manages to hold him off using both his ice and fire powers. However, the Hero Killer's highly adept combat skills pressurizes and nearly overwhelms Shouto. Suddenly, Izuku activates One For All Full Cowl and leaps in to stop the Hero Killer's attack; Stain retaliates by knocking Izuku away with his elbow. Izuku and Shouto fall back. The two young Heroes start to realize that the Hero Killer's immobilization Quirk has to do with blood types to which Stain states that they are correct. Izuku and Shouto begin strategizing with Shouto stateing that they will protect Tenya and the Pro Hero. Tenya starts to feel regret for his actions as he has not been acting like a Hero should be.

Izuku and Shouto team up to battle Stain. Izuku activates One For All Full Cowl and tries to attack the Hero Killer, but Stain slashes at Izuku with his katana, causing Izuku's leg to bleed; Stain licks his katana and activates his Quirk, which paralyzes Izuku; Izuku apologizes to Shouto as Tenya tells them to stop. Shouto replies that if Tenya wants to stop them he must stand up. Now that Izuku is immobilized, Stain sets his sight on Shouto; he cuts through Shouto's wall of ice, removing Shouto's defense and prepares to attack Shouto. Shouto encourages Tenya to be the man he wants to be. Tenya remembers that he wants to be like his brother, Ingenium and tries to break free of Stain's Quirk.

Tenya's Newfound Resolve: The Final Battle Against Stain
Tenya is ashamed that he needs protection from his friends, Izuku and Shouto. Tenya remembers his brother's motivation for being a Hero; that helping people is the best motivation for being a Hero. Shouto attacks Stain with a stream of ice concealed in it is fire but Stain dodges. Stain criticizes Shouto for relying on his Quirk too much and prepares to cut Shouto with his katana. Tenya agrees with Stain; that he is a failure as a Hero and pales in comparison to Izuku and Shouto. Stain's Quirk wears off and Tenya gets up with the motivation of not wanting to be outpaced as a Hero by Izuku, Shouto and his brother. Tenya uses Recipro Burst and smashes his leg into Stain's katana, shattering the katana in half and saving Shouto in the process. Tenya then kicks Stain away.

Tenya apologizes to Izuku and Shouto for getting them involved in his problems, not wanting them to spill anymore blood for his sake. Stain criticizes Tenya for having a change of heart, saying that a man's character never changes and that Tenya is a fake Hero who prioritizes selfish desires; Stain says that people like the selfish Tenya are the "cancer" of society and that he is here to correct that. Shouto tells Tenya to pay no heed to Stain, but Tenya says that Stain is correct about him not being a true Hero. Tenya tells Stain that he cannot give up so easily as doing so means that Ingenium would die, much to Stain's anger.

Tenya asks Shouto to cool down his leg, but Stain attacks Shouto with daggers to which Tenya intercepts and falls down to the ground. Izuku regains his mobility and activates One For All Full Cowl, jumping off Shouto's ice platform towards Stain. Shouto cools Tenya's leg, restoring Tenya's mobility. Tenya uses Recipro Extend and leaps into the air towards Stain. Shouto encourages Izuku and Tenya to press forward with their attacks; Izuku punches Stain in the face with his enhanced might while.Tenya hits Stain in the stomach with his speed enhanced kick.

Izuku's enhanced punch and Tenya's Recipro Burst hit Stain. The combined might of Izuku and Tenya's attacks causes Stain to lose consciousness. However, Stain keeps himself awake and makes one last ditch attempt to kill Tenya by attacking Tenya with a blade. However, Tenya kicks Stain again and Shouto shoots a stream of fire at Stain's face, burning the Hero Killer's face. Shouto and Tenya's additional attacks causes Stain to reach his limit, becoming unconscious and falls onto Shouto's ice, defeated. Shouto creates an ice ramp so that Izuku and Tenya can land safely. Izuku, Shouto and Tenya remove Stain's weapons and tie him up.

The Hero Killer Defeated!: Hosu's Chaos Begins to Subside
At the other battlefield, the Noumu-like creature absorbs and releases Endeavor's flames but Endeavor mocks the creature's Quirk and pitiful attempt. However, Gran Torino tells Endeavor to be aware of the Noumu-like creature as it possesses multiple Quirks. The Noumu-like creature prepares to attack Endeavor with a tongue-like Quirk. Suddenly, Gran Torino propels himself at a great speed and smashes down into the Noumu-like creature, defeating it. Endeavor decides to let his sidekicks restrain the Noumu-like creature and tells Gran Torino to go to the address that he will give him.

Izuku, Shouto, Tenya and the Pro Hero leave the alley with the unconscious Stain in tow being pulled by Shouto. Tenya asks Shouto if he can be the one who pulls Stain to which Shouto denies Tenya's request due to Tenya's arm being badly damaged; the Pro Hero laments about being a burden but Izuku eases his worry since no one can defeat Stain in a one-on-one battle due to his Quirk. Gran Torino arrives at the address Endeavor gave him and encounters Izuku's group who have defeated the Hero Killer Stain. Gran Torino propels his foot into Izuku's face, annoyed that Izuku did not stay put. However, he is relieved that Izuku is alright. Then, Endeavor's sidekicks arrive. Tenya apologizes for his un-heroic actions with Izuku saying that he is also sorry for overlooking his pain; Shouto tells Tenya to pull himself together because he is the Class President with Tenya complying.

Suddenly, the winged Noumu-like creature appears in the sky. Gran Torino sees the winged Noumu-like creature above and commands everyone to duck. The winged Noumu-like creature grabs Izuku and prepares to fly away. Gran Torino prepares to propel himself into the air to rescue Izuku and Shouto prepares his fire.

Stain's Resolve: The Hero Killer Stands Tall!
Shockingly, Stain regains consciousness and frees himself from the ropes with a blade up his sleeve. Stain licks off the winged Noumu-like creature's blood from the female Pro Hero's face and activates his Quirk. The winged Noumu-like creature becomes paralyzed due to Stain's Quirk and stops flying, dropping Izuku in the process. Stain stabs the winged Noumu-like creature's brain and defeats it, causing to fall to the ground. Stain grabs Izuku and saves him. Stain, despite being heavily injured, states that the "fake" Pro Heroes and the pathetic criminals in society are his targets for his purge, saying that everything he is doing is for a just world. Izuku and the Pro Hero who was injured by Stain are shocked at the Hero Killer's actions.

Meanwhile, Tomura is watching the events unfold and is displeased that nothing is going his way. Endeavor arrives and sees the Hero Killer; Endeavor prepares to launch an attack on Stain to which Gran Torino tries to make him stop.

Stain's bandaged mask falls off, revealing that he does not have a nose, shocking everyone. Stain, despite his heavy injuries, steps forward and states that the fake Heroes must be rectified and the word Hero must be restored. Stain urges the "pretenders" to try and stop him. Stain continues walking forward and declares that the only one who is allowed to kill him is All Might. Stain unleashes a bloody malefic aura which instills fear into everyone present; one of the Pro Heroes fall down out of fear, Shouto and Tenya fall to their knees, Izuku becomes terrified, Gran Torino becomes tense and even Endeavor takes a step back. Stain takes a step forward, but the grievous injuries of his perforated lungs due to his broken ribs causes Stain to finally lose consciousness. Everyone is shocked and stunned that even though the Hero Killer lost consciousness, Stain is still standing.

The next day at the Hosu General Hospital, Izuku, Shouto and Tenya are recuperating. Izuku concludes that Stain allowed them to live as he had the power to kill them at any time to which Shouto agrees. Shouto tells Tenya that his bravery helped save the day but Tenya admits that he doesn't deserve any praise. Manual and Gran Torino announce to the young Heroes that they have a visitor; The Chief of the Police Force; Tsuragamae Kenji, a tall looking human with a dog-like face.

Tsurugamae tells the young Heroes them about Stain's condition; that he has severe injuries but is alive and is being treated. He then begins to tell them that since the appearance of Quirks the police refused to use Quirk users in the Police Force out of fear that Quirks would be used as weapons and that was why Heroes were rose up to fill that position, but only if they followed strict rules and morals, as even young heroes like them that aren't ready to take such roles may harm other with their Quirks if they aren't with their guardians or supervisors. Even if it was the Hero Killer, it would still be consider breaking the law, as such because the young Heroes were not with their supervisors during yesterday's incident, Tsuragamae tells them that they and their guardians (Manuel, Endeavor and Gran Torino) must receive punishment for breaking the law.

Furious, Shouto says that had they not gone into action Tenya and Native would have been killed by Stain; Shouto prepares to lash out at the Chief of Police, angry that he expected them to sit idly and do nothing but obey the law; Gran Torino and Tenya stop him. Tsurugamae says that was just his opinion as a member of the Police Force, as stated that they would have been punished had it been an official disclosure. Since there were not enough witnesses to report the incident regarding Stain, Tsuragamae states that he will cover up the incident but as a result Izuku, Shouto and Tenya will not get any recognition for their valiant efforts. Tsuragamae admits that he is covering up the story because didn't want the young Heroes to get into trouble. Izuku, Shouto and Tenya thank the Chief of Police. Tsuragamae says that Izuku, Shouto and Tenya have a promising future awaiting them; Tsuragamae gave them a bow for their heroic actions and thanked them for keeping the peace.

Stain's Past and Ideology Revealed: An Old Nemesis Returns
The next day begins; the news of Stain's defeat and arrest spreads like wildfire throughout Japan. At the Villain Alliance Hideout, Tomura reads the newspaper. However, the newspaper mainly publishes Stain's feats and that his name will go down in history while the news on the Noumus is undermined. Angry that Stain is all over the news, Tomura crumbles up the newspaper, dissatisfied that his plan to undermine Stain and make the world forget about him failed. Tomura is annoyed by the fact that the world will never forget about Stain and that his efforts were undermined.

Elsewhere, Katsuki thinks heavily about the incident to which Best Jeanist admits that he is also is thinking about it; he informs Katsuki and his sidekicks that they must stay calm and decides to take it easy. Eijirou and Tetsutetsu are preparing to meet with Force Kind. Momo, Itsuka and Uwabami work on a demo commercial before heading out to patrol. Ochako phones Izuku to talk to him and is relieved that he and Tenya are alright; she begins training with Gunhead.

At Hosu General Hospital, Tenya informs Izuku that his left hand is greatly injured but can be probably healed through surgery. However, Tenya states that he has decided to leave his left hand in its injured state as a reminder of his un-heroic actions so that he will not make the same mistake twice. Izuku, seeing that Tenya understands his mistake, tells Tenya that they must strive to become stronger so that they never injure themselves again. Shouto apologizes and states that because he is always involved people's hands go bad; Izuku and Tenya are surprised that Shouto can make a joke but Shouto replies that he is serious, causing the three young Heroes to laugh.

Gran Torino speaks to All Might using a telephone. Gran Torino states that Izuku has improved drastically with his usage of One For All; All Might apologizes to Gran Torino for getting him into trouble and thanks him for teaching and helping Izuku while also apologizing for his inadequate teaching. Gran Torino tells All Might why he is calling; Gran Torino says to All Might that Stain's ideology is identical to All Might's; that both ideologies have charisma which can be used to inspire people. Gran Torino states that he fears that if Stain's backstory and ideology is revealed to the public, it will inspire villains to rise up and the Villain Alliance will take all the credit since the public views the Villain Alliance as a group that follows Stain's ideology which will cause new villains to join the alliance; thus evil will grow. 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 shocked that "All For One" has probably 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. Gran Torino ends the call.

Two days later, Stain's backstory is spreading throughout Japan and has become a main topic. In a hostess bar, two men are talking; a large man states that crime has taken a turn for the worse ever since All Might appeared and decides that he might retire. However, a man smoking a cigarette tells the large man to hold off his retirement; he shows the large man a video detailing Stain's backstory and his last stand before being arrested. The man with the cigarette says that Stain's attitude before falling unconscious will inspire hundreds of people including many criminals as well as himself. The man with the cigarette states that many new villains will show up and unite with the organization that Stain was believed to be apart of: the Villain Alliance.

Workplace Training Ends
At the end of the week, workplace training comes to an end. Outside Gran Torino's apartment, Izuku thanks Gran Torino for looking after him and training him; Izuku praises Gran Torino for his training as it has allowed him to become stronger. Gran Torino advises Izuku to maintain his control and composure when using One For All and to not go over the 5% limit. Izuku says that he will comply. Izuku asks Gran Torino a question; why a strong Hero like him isn't known by society. Gran Torino replies that he wasn't interested in the Hero life and that the only reason he became a certified Hero was for a certain goal and nothing else. Gran Torino tells Izuku to ask All Might about the whole story. As Izuku leaves, Gran Torino ponders that both All Might and Izuku are alike; having the same charisma. Gran Torino asks Izuku his name; Izuku thinks than Gran Torino went back to being senile, but realizes what he wants as an answer. Izuku tells Gran Torino that his name his Deku. Gran Torino smiles at the response, turns around and goes back into his apartment.

At Yuuei in Class 1-A, everyone talks about their workplace experience. Afterwards, Class 1-A attends their next class; 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. The class comments on who will win; Momo and Kyouka note that Izuku is at a disadvantage due to his grievous Quirk with Katsuki saying that Izuku will lose; others think that Tenya, Ojiro, Sero and Mina all have an equal chance at winning.

The race begins; Izuku activates One For All Full Cowl and begins maneuvering through the construction site with ease; using his enhanced  speed and agility to jump and move through the construction site. All Might, Shouto and Ochako note his extraordinary movements while the rest of the class are surprised by Izuku's skills. Katsuki is shocked that Izuku's movements in combat have become similar to his own, angry that Izuku has improved so much. However, while moving towards the area, Izuku accidentally slips, causing him to lose his lead and arrive last while Hanta places first After the race ends, All Might commends the group on improving their Quirks more broadly since entering Yuuei. 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.

The Origin: All For One and One For All
Foundational Hero Studies end and Izuku changes into his school uniform. Afterwards, Izuku heads to the Break Room to meet with All Might. 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 doesn't 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 won't 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 braindead 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 Quirkless 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 Villain Alliance. 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 older brother.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 isn't able to bring himself to tell Izuku the truth and thanks him instead; All Might isn't able to reveal that he probably won't be by Izuku's side when the time comes.

Class 1-A's Next Destination: True Evil Manifests Within The Shadows
Izuku returns to class, where Shouta tells Class 1-A that they will be going to a forest lodge during the summer break. However, Shouta warns his students that if any of them fail to pass the end of term test, then they will be stuck in remedial school.

Elsewhere, a man is surprised that the Hero Killer Stain was captured but is still happy that things are going as he has foreseen. He exclaims that Tomura's position is to supervise and unify the new villains who have come to join the Villain Alliance. The man's doctor expresses doubt if Tomura can do his job and says that if the man stepped in things would be proceeding faster. The man asks the doctor to patch him up faster. The man reveals himself to be Tomura's sensei (the man who possesses All For One) and says that he will let Tomura do all the hard work so that he may become his successor as Tomura was born to do so. Sensei tells All Might to rejoice in the "transient" peace while he still can.

Story Impact

 * Gran Torino, a former Pro Hero and former teacher at Yuuei as well as friends with All Might's predecessor, makes his debut, requesting Izuku to train with him to gain work place experience and to train him in using One For All better.
 * Izuku Midoriya learns more about One For All and the nature of Quirks during his training with Gran Torino and gains the ability to use One For All more efficiently, no longer needing to break his bones in order to use it.
 * Shouto Todoroki begins using his Fire side more frequently and holds his grudge against Endeavor aside.
 * New Quirks are revealed:
 * Stain's Quirk; he has the ability to immobilize his victims for a period of time (depending on the victim's blood type) by ingesting their blood.
 * Gran Torino's Quirk; he has the ability to shoot air air from the propulsion boosters at the bottom of his feet.
 * Tsuragamae Kenji first shows the contradictory laws for Pro-Heroes which affects the publicity of one of the events in this arc.
 * The origin of One For All is revealed.

Characters Introduced

 * Chizome Akaguro
 * Crimson Riot
 * Gunhead
 * Gran Torino
 * Normal Hero
 * Best Jeanist (First Appearance)
 * Force Kind
 * Uwabami
 * Native
 * Tsuragamae Kenji

Battles

 * Gran Torino vs. Noumu
 * Tenya Iida & Izuku Midoriya vs. Stain
 * Tenya Iida, Izuku Midoriya & Shouto Todoroki vs. Stain