Vs. Hero Killer Arc

Also called the Field Training Arc, this is the sixth story arc of My Hero Academia and the sixth of the U.A. Beginnings Saga, covering Chapters 45 to 59 and Episodes 26 to 33. It follows the U.A. Sports Festival Arc and precedes the Final Exams Arc.

Professional heroes nominate students for week-long internships. Izuku Midoriya is claimed by Gran Torino, All Might's former homeroom teacher, while Hosu City becomes the stage for the Hero Killer's campaign, a League of Villains rampage, and the first honest account of where One For All came from.

Class 1-A chooses hero names under Midnight's judgment. Tenya Ida cannot bring himself to take his brother's title, Ingenium, and uses his own name instead. Izuku claims Deku, because someone changed what the word meant to him. Katsuki's every suggestion is rejected. Aizawa notes that Tenya passed over better offers for the Hosu City Hero Office, which is not a coincidence.

Izuku arrives to find Gran Torino apparently dead on the floor in a puddle of ketchup, forgetful and infuriating, until a demonstration of speed reveals the real man underneath. Their sparring exposes the problem: Izuku treats One For All as a special trump card, which makes him rigid. The fix is to think of it as a body function. A badly heated taiyaki gives him the second half, that he has been running the power through one part instead of all of him, and Full Cowl follows.

Kurogiri brings Stain to meet Tomura Shigaraki. The Hero Killer overpowers him instantly, lectures him on creeds, and is impressed only when Tomura disintegrates his dagger while admitting he simply wants to grind All Might's society into the dirt. Stain concludes their desires overlap enough to leave the League standing, and orders a warp back to Hosu, where business waits.

Tomura, sick of the preaching, releases three Nomu on the city. Gran Torino tackles one out of a moving train and leaves Izuku behind, who runs toward the fire anyway once he realizes Tenya must be hunting Stain alone. Tenya finds him standing over the hero Native, announces himself as the brother of a man Stain cut down, and is beaten, stabbed, and paralyzed by Bloodcurdle. Izuku's Full Cowl punch arrives first, Shoto Todoroki arrives second after a vague text, and the three of them work out that the immobilization requires blood and varies with blood type. Tenya, ashamed, finally remembers that his brother became a hero to help people rather than to be avenged, breaks free, shatters Stain's katana with Recipro Burst, and joins the combination attack that puts the Hero Killer down.

Endeavor and Gran Torino dispatch the creatures between them, burning one skull to carbon so it cannot regrow, but the winged one snatches Izuku from the group. Stain wakes, frees himself, paralyzes the creature with borrowed blood, kills it, and catches Izuku. His mask falls away, revealing the missing nose, and he declares that fakes must be purged and only All Might may kill him. The aura of intent alone drops a professional to the ground and makes Endeavor step back, and then his perforated lungs finish him. He loses consciousness still standing.

Police chief Kenji Tsuragamae explains that the students used their Quirks without supervisors and are technically criminals, and that their guardians would share the punishment. With too few witnesses to force an official disclosure, he buries the incident. Endeavor is credited with the capture, and Izuku, Shoto, and Tenya get no recognition and no charges. Tenya refuses surgery on his ruined left hand, keeping it as a reminder.

The cover-up does not contain the ideology. Stain's backstory spreads across Japan within days, and Gran Torino warns All Might that the man's convictions have the same charisma as his own, that they will inspire criminals, and that the League will absorb the credit. He names his suspicion: All For One, whose hands took the life of All Might's own master and carved the scars into his side, has come back. In a bar, a smoking man shows a colleague the footage and predicts exactly that.

All Might tells Izuku the origin. In the chaotic early days of Quirks, a man with a power that steals and bestows Quirks conquered Japan. He forced a stockpiling Quirk onto his supposedly Quirkless younger brother, who already carried a Quirk that transfers itself, and the two merged into One For All. The brother could not beat him and passed the power down instead, generation after generation, until All Might believed he had finished it. He has not. Izuku, the ninth holder, will have to face the older brother too, and All Might cannot bring himself to say he will not be there.

Aizawa announces a summer forest lodge, contingent on passing end of term exams. In a hidden room, All For One tells his doctor to patch him faster, sets Tomura to unifying the new villains flocking to Stain's banner, and invites All Might to enjoy what peace remains.