U.S.J. Arc

Formally the Unforeseen Simulation Joint Arc, this is the fourth story arc of My Hero Academia and the fourth of the U.A. Beginnings Saga, covering Chapters 12 to 21 and Episodes 9 to 13. It follows the Battle Trial Arc and precedes the U.A. Sports Festival Arc.

Class 1-A travels to a purpose-built training complex to practice rescue work. The League of Villains, having already breached the school's security once, is waiting for them, and their stated goal is to kill the Symbol of Peace.

Reporters swarm U.A. hunting All Might stories. Class 1-A elects Izuku Midoriya president and Momo Yaoyorozu vice president, but when a siren empties the cafeteria in a panic, Tenya Ida floats himself into the air and calms hundreds of students with a shout. Izuku promptly resigns in his favor. The faculty finds the barrier disintegrated and concludes the intrusion was deliberate, possibly a declaration of war.

At the Unforeseen Simulation Joint, Thirteen explains that the day's lesson is about using Quirks for human life. Then a black portal opens and villains pour out, complaining that their stolen curriculum promised All Might would be present and wondering whether killing children would summon him. Shota Aizawa charges in alone and dismantles them, while Kurogiri blocks the exit and warps most of the class into separate zones.

In the Flood Zone, Tsuyu Asui pulls Izuku and Minoru Mineta onto a ship. Izuku works out that the enemy has no data on their Quirks and turns that into a plan: a Delaware Smash parts the water, Tsuyu hauls him clear, and Minoru's spheres glue the converging villains into one helpless mass. Shoto Todoroki freezes the Landslide Zone solid on his own. In the Mountain Zone, Momo's insulating sheet lets Denki Kaminari discharge across everyone at once. Katsuki Bakugo and Eijiro Kirishima clear the Ruins Zone and go looking for Kurogiri, reasoning that the gateway is the League's real asset.

Thirteen loses to Kurogiri, whose warp turns Black Hole back on her, but Mezo Shoji and then Ochaco Uraraka buy Tenya the seconds he needs to reach the exit and run for the school. At the Central Plaza, Tomura Shigaraki begins disintegrating Aizawa's elbow, and a creature called Nomu pins him to the ground. Izuku's punch lands on Nomu and does nothing.

All Might arrives, clears the plaza at speed, and carries the wounded to safety. Carolina Smash accomplishes nothing against Shock Absorption, and a suplex only invites Kurogiri to trap him at his weak spot. Katsuki pins the mist villain by his neck plates, Shoto ices half of Nomu, and All Might breaks free. Tomura calls the Symbol of Peace an oppressive form of violence; All Might calls that rubbish and pushes past his own limit, punching Nomu clear out of the building.

With Nomu gone, Tomura panics until Kurogiri points out how much damage All Might has already absorbed. They charge, Izuku launches himself to intercept, and Snipe's bullet stops the attack cold. The teachers have arrived with Tenya. Thirteen, barely standing, opens Black Hole on both villains, and Tomura promises a next time before vanishing into it.

Everyone survives. Cementoss walls Eijiro off before he can see All Might's true form, and Naomasa Tsukauchi reports the teachers and Izuku as critical but not dying. All Might insists the students fought bravely and will make fine heroes. In the League's hideout, Kurogiri and Tomura reappear, having warped clear at the last instant. A voice through a blank monitor tells Tomura he was over-optimistic rather than wrong, dismisses mourning for Nomu, and promises the world will learn the horror of his existence.

The next day Aizawa walks into class wrapped in bandages and tells the students their fight is not over, because the Sports Festival is next. All Might has begun to weaken noticeably, Aizawa's Erasure is diminished, and Eijiro's friendship with Katsuki has quietly begun.