U.A. Traitor Arc

The U.A. Traitor Arc is the twenty-first story arc in My Hero Academia, and the third story arc in the Final Act Saga.

The pieces are in place and Class 1-A and the remaining Pro Heroes are preparing for the final fight to take down All For One, Tomura Shigaraki, and the rest of the League of Villains/Paranormal Liberation Front for good. However, things become complicated when the fabled "U.A. Traitor" suddenly emerges...

A Mighty Force, A Weaving Plot
Following Tomura Shigaraki's disappearance after his battle with No. 1 American Pro Hero, Star and Stripe, All Might reveals to Class 1-A that, based on the data gathered by the American fighter jets, Star and Stripe's Quirk, New Order, acted like a poison when Tomura stole it, eating away at him and ravaging a considerable amount of his Quirks. The class realize that now is the best possible time to take him out. All Might continues, saying that the remaining Heroes have been continuing the mass evactuation effort whilst hunting down the remaining Villains, reminding them that, due to how predictable All For One is, all out war is inevitable.

All Might reminds the class of the targets that remain: Tomura, All For One, Dabi, Himiko Toga, the six Near High-End Nomu that remain, the remnants of the Paranormal Liberation Front, and the remaining escaped convicts. He goes on to say that they will likely amass more allies. He continues, saying that, while less than half of their heroes remain, it is thanks to Star's sacrifice that they have a chance to use this time to grow even a little stronger.

In response to this, Katsuki shouts at All Might that they have been doing this already. The class reveal to All Might that since the Paranormal Liberation War, they have continued their training with the the Wild, Wild Pussycats, with the intention of fighting alongside Izuku until Tomura is defeated. Izuku says that Katsuki and the others agreed to spar with him to help master One For All, but Katsuki claps back in his usual fashion, claiming that he only wants to test his new Cluster moves on him.

The rest of the class respond with enthusiasm as they prepare to head out and train. All Might watches on, thinking about how the "zygotes" from the first day have hatched into fledgling heroes, braving all that comes their way. He thinks on, claiming that All For One has made a foolish error and that Class 1-A is a mighty force to behold.

Meanwhile, screaming in pain, "Tomura" returns to the League of Villains' secret base. All For One tells him to calm down, as their Quirk Factors are damaged and need time to heal, but his order is met with obscenities, with "Tomura" saying that as long as people remember All Might, he'll never know peace. All For One notes that, since their minds have fused, he shares the hatred "Tomura" possesses. All For One tells "Tomura" that, even though they couldn't steal New Order, they have eliminated their biggest obstacle and they need to take it easy for the time being.

He tells the League to remain on standby for a bit longer, but Dabi responds in opposition, saying he can't stand the sight of still seeing his dad flying around. All For One tells him that, while they are very alike, they have one crucial difference. While Dabi may have one goal set in stone in his mind, he has planned out and weaved together many different routes over the decades, all to eventually reach his final goal. He tells the fire villain that because the perfection of Tomura's body has been delayed and that the fortified U.A. has welcomed Izuku back, he has something that Dabi lacks: "friends to spare." Back at U.A., Toru Hagakure stands in the shadows, observing someone.

From the Shadows: the U.A. Traitor Emerges
Class 1-A continue to train amongst themselves in one of the courtyards of U.A. Katsuki talks about how he learnt the "build up and release" mechanic from his internship with the Endeavor Agency, but is now focused on saving up a bunch of sweat, so rather than one big Explosion, he can create a whole barrage of explosions simultaneously to power his new Cluster technique. He is also wearing his winter suit to increase his sweat production. Izuku notices Shoto taking a different approach as well, as Shoto says he has now reached the point where his control over the left side of his body has caught up to that of his right, so now he needs to make both sides into one to create a body that even Dabi cannot burn.

Denki discusses with Minoru about how, with Tomura and All For One both currently weakened and with Gigantomachia still sedated, the fight should be easier for them, but Katsuki says there are three reasons why they are wrong. The first reason is that even after being able to locate the research facilities and hideouts, the Heroes were never able to track down All For One himself, saying that he is "the world champ at hide-and-seek."

Momo steps in with the second reason, saying that Tomura was incomplete in the previous battle and that they're only working with half of the Heroes now. Katsuki says the third reason, which is that the villains will be the one to decide when the battle starts, as even if the Search Quirk was destroyed, they still get to make the opening move, which is why they are calling every able body to arms and that sheer numbers will give them a chance.

Izuku states that if they can do nothing else, the least they can do is steer the villains' next moves in the heroes' favour and that he should rejoin the search as well. Tenya reprimands Izuku, reminding him that "we" will be rejoining the search. Izuku looks around and asks Tenya if he can go for a quick stroll, with Tenya replying in the affirmative as relations between the students, Heroes, and evacuees have improved following Ochaco's speech. Denki remarks that, even with his back against the wall, All For One's continues to wear a grin on his face.

While this is happening, in the U.A. Forest, Toru is investigating someone, having noticed that "he" has been looking down ever since the War, while also noticing that, since Izuku's return to U.A., "he" hasn't smiled once. Two voices in the distance tell someone that they just received another order from "him", and to keep listening like they always have. A tearful Yuga Aoyama listens to his parents as they remind him that he has to do what All For One, lest they all be killed.

Reacting in shock, Toru realizes that Yuga has been the fabled "U.A. Traitor" all along. Yuga's parents hysterically try to reassure Yuga, reminding him of how he was able to inform All For One about the location of the training camp without being exposed. They talk about how they only ever wanted to give their son a shot at happiness in life. They also talk about they wanted to help him fit in as he was born Quirkless. They say that, had they known how bad things would have gotten, they would have never done it, but the moment Yuga got his Quirk from All For One, they were trapped under his thumb with no way of escaping. Now in panic, Toru thinks about needing to tell someone, when she spots someone else nearby.

Yuga talks about how he had to play his part in order to avoid being exposed and that he had to put on a brave face so as to not be completely crushed by guilt. When All For One was defeated and caught in Kamino, he talks about how he mistakenly let himself think that he was free from the tyrant's clutches, with his parents begging him for his forgiveness. Yuga cries out saying that he only wanted to protect his parents and that he will not let them be killed, as his parents call out for their son to save them.

The tearful family are startled when they hear a rustle in the woods, seeing Toru with Izuku, who has heard some of the details from her. Yuga's parents attempt to feign ignorace, while Yuga thinks about how when 1-A went to bring Izuku back to U.A., he was the only one who was silent. Izuku tells his classmate that he has noticed how gloomy he's been looking and came looking for him, believing that something was wrong. Hearing his words, Yuga, through tears, admits to Izuku that he was the one who helped the League during the U.S.J. Incident, as well as the Training Camp, declaring himself a "despicable villain."

Story Impact

 * All Might reveals to Class 1-A that Star and Stripe's New Order Quirk has destroyed several of Tomura's Quirks after he stole it, giving them and the rest of the Heroes time to prepare to deal with the remaining threats.
 * These threats include: Tomura, All For One, Dabi, Himiko Toga, the six Near High-End Nomu, the remnants of the Paranormal Liberation Front, and the remaining escaped convicts, in addition to any additional allies they may gain.
 * It is revealed that since the end of the War, the students of Class 1-A had continued their training with the Wild, Wild Pussycats to get stronger.
 * "Tomura" is forced back on standby to allow his damaged Quirk Factors to heal.
 * Tomura and All For One's minds continue to fuse together, sharing their feelings of hatred.
 * Himiko is revealed to have reunited with the League.
 * Dabi remains impatient, wanting to go after his father again, before being talked down by All For One.
 * All For One confirms that he has a mole within U.A.
 * Class 1-A continue their training.
 * Katsuki Bakugo has developed a new technique to make use of his Cluster move, saving up a bunch of sweat for a barrage of explosions, all while wearing his winter costume.
 * Shoto Todoroki has reached the point where control over his left side has caught up to his right, so now he's focusing on using both at the same time.
 * Gigantomachia is confirmed to still be tied up and unconscious.
 * The "U.A. Traitor" is revealed to be Yuga Aoyama.
 * He was born Quirkless, and with his parents both coming from wealthy backgrounds, they made a deal with All For One to give him his Navel Laser Quirk in a desperate move to grant their son a happy, successful life.
 * He possessed the Quirk for ten years, which was incompatible with his body.
 * Because of the deal, the Aoyamas were forced to comply with All For One's orders against their will, or else they would face dire consequences.
 * All For One told Yuga to enroll in U.A. after learning All Might would become a teacher.
 * He provided information aiding in isolating the class during the U.S.J. Incident, as well as providing the location of the Summer Training Camp.
 * His parents receive another order from All For One, for Yuga to isolate Izuku Midoriya away from everyone, tearfully apologizing to him to do it.
 * Toru Hagakure and Izuku overhear the Aoyamas discussion and confront him, as he tearfully confesses to the truth.
 * Izuku restrains Yuga and his parents before they can escape.
 * Toru's face is briefly revealed for the first time in the confrontation.
 * Class 1-A, the U.A. Staff, and the Police Force discover the truth about the Aoyamas, where they are put under interrogation.
 * The Aoyamas reveal All For One's threats of death were they to say anything to the Police.
 * Izuku extends his hand to Yuga, stating he knows he never had any villainous intentions, proclaiming he can still be a hero.
 * Class 1-A states their intentions of wanting to forgive Yuga for his actions so he can help them take down All For One.
 * Shota Aizawa sides with his class, coming up with a classified plan to make use of Yuga.
 * The Aoyamas are taken to Central Hospital for further study.
 * Izuku and Tenya Ida encounter Mei Hatsume again at the Development Studio to fix up their hero costumes.
 * The Support Course is revealed to be in charge of developing and maintaining the U.A. Barrier.
 * Mei is in charge of creating new inventions to assist in the case of mass evacuation.
 * Mei creates a new makeshift Gauntlet out of the remains of Izuku's Mid-Gauntlets and his Air Force Gloves.
 * The Class 1-A Search Squad assembles to track down the remnants of the League of Villains and the Paranormal Liberation Front.
 * At the same time, a Counter-Force assembles at Central Hospital, consisting of All Might, Hawks, Ragdoll, Naomasa Tsukauchi, the Police Force, and Star and Stripe's American brothers-in-arms.
 * Their plan is to separate Tomura and All For One by at least 10 kilometers to prevent them from combining their power.
 * This also involves isolating all major operatives of both the League and Liberation Front, and taking them out one by one, so that they will be unable to assist either.
 * Yuga is interrogated by Shota, where it's confirmed he does not possess an explosive trap like Lady Nagant had.
 * Shota theorizes only people All For One had contact with after his defeat from All Might could potentially have an explosive trap within.
 * Shota manages to convince Yuga to help them fight back, telling him not to let the guilt ruin the rest of his life.
 * Hitoshi Shinso's hero costume is revealed.
 * Himiko visits her old family home, now abandoned and heavily vandalized, while reminiscing about her past.
 * Himiko leaves and encounters Dabi who questions if she's ready to help the villains bring an end to society before burning down her old home.
 * It is revealed that Dabi acquired a sample of Twice's blood during the War, and gives it to Himiko, allowing her to Transform into him and utilize his Double Quirk.
 * "Tomura" continues through his process of recovery.
 * It seems that the lost fingers on his left hand are starting to grow back.
 * Spinner reluctantly agrees to take the lead as the face of the Paranormal Liberation Front, to steer the heteromorph villains toward their cause.
 * Spies for All For One are revealed to be within U.A.'s walls, with the intention of spurring discourse amongst the public to drive Izuku out.
 * All Might, Naomasa, and Nezu inform Class 1-A of their plans for the second War.
 * At the same time, Hawks and Ragdoll inform Endeavor and Best Jeanist of said plans.
 * Nezu announces to the evacuees of Tomura's upcoming completion in 4 days.
 * Class 1-A move into a make-shift fortress "Troy" to prepare.
 * Izuku thanks Ochaco for her speech to the public.
 * The two of them trade their thoughts about wanting to understand Himiko and Tomura.
 * Shoto also talks about wanting to understand Toya.
 * The day of the operation is reached.

Characters Introduced
No new characters are introduced this arc.

Quirks Introduced
No new Quirks are introduced this arc.

Battles & Events

 * Deku & Invisible Girl vs. Can't Stop Twinkling