Plot
Izuku "Deku" Midoriya is a Quirkless boy who, despite his lack of powers, dreams of becoming a Hero and attending U.A. High School, idolizing Japan's No. 1 Hero, All Might who also attended U.A. He is frequently picked on by others for this, particularly his childhood friend Katsuki Bakugo. One day, All Might witnesses Deku attempt to save Bakugo from a villain, making him choose Deku to inherit his Quirk "One For All"—which gives him the ability to stockpile his raw power and pass it on to others—and become his successor. All Might was severely injured by his arch-nemesis All For One, whose Quirk allows him to steal other Quirks for his use and pass them over to others at his will. After nearly a year of physical training, Deku inherits One For All and passes the entrance exam to U.A. by saving Ochaco Uraraka. Deku, Ochaco, and Bakugo are among the twenty students placed in Class 1-A, where Deku's tenacity earns him several friends. During one of their classes, Class 1-A encounters the League of Villains, led by All For One's apprentice Tomura Shigaraki. Shigaraki attempts to use an artificial being called a Nomu to kill All Might, but All Might overpowers it.
Class 1-A takes part in a sports festival with the rest of their grade. During this, Deku helps his classmate Shoto Todoroki move on from his resentment of his father–the No. 2 Hero Endeavor–for mistreating him and his family. As the sports festival ends, 1-A's Class Representative Tenya Ida's older brother is crippled by Stain, a villain who believes most heroes only desire fame. As the U.A. students go on their Hero Agency internships, Ida finds Stain and attempts to get revenge, though Stain is ultimately defeated by Deku and Todoroki. Stain's ideology spreads, and many of his believers join the League of Villains, including Dabi, Himiko Toga, and Twice. After the class finishes final exams, the League of Villains' recruits ambush Classes 1-A and 1-B while they are training at a summer camp, and kidnap Bakugo in the hopes of recruiting him. All Might leads several heroes in locating the League of Villains' hideout, where All For One reveals himself. Deku and some of his friends rescue Bakugo as All Might battles All For One. All For One is defeated and imprisoned, but All Might exhausts the last of One For All's power and retires. Endeavor, now the No. 1 Hero, is humbled by his added responsibility and begins trying to make amends with his family.
The class partakes in their Provisional Hero License Exam, which Todoroki and Bakugo fail and take remedial courses handling children with powerful Quirks. Afterwards, Class 1-A meets with the "Big Three", U.A. High School's top-ranked seniors who select a few Class 1-A students to join them as interns; one of the Big Three, Mirio Togata selects Deku to join his internship with All Might's former sidekick Sir Nighteye. Nighteye's team comes into conflict with the Shie Hassaikai, a yakuza group formerly allied with the League of Villains who are experimenting on their boss's granddaughter Eri to produce Quirk-Destroying Drugs. Nighteye leads his agency, alongside those of the other Big Three, in a raid to save Eri, during which Nighteye is killed and Mirio is de-powered. Eri is taken in by the U.A. staff, and Class 1-A performs a rock concert for her during the school culture festival. During a battle exercise with Class 1-B, Deku begins to awaken all of the Quirks used by the previous users of One For All. He eventually continues his internship under Endeavor, alongside Bakugo and Todoroki.
The League of Villains defeats and merges with another villain group, the Meta Liberation Army, forming the Paranormal Liberation Front. A war ensues between the Paranormal Liberation Front and the pro and training heroes; Twice is killed by the new No. 2 hero Hawks, but most of the remaining top members escape, including Shigaraki, who now inherits All For One's Quirk and is possessed by him. Mirio is re-powered by Eri, and joins the heroes partway through the war. Ochaco develops sympathy for Toga after the latter interrogates her about Twice's death. Dabi reveals himself as the presumed-dead son of Endeavor, whose abuse led him to villainy, which in combination with the collateral damage of the war, shatters the public's trust in heroes. Thousands of imprisoned Villains break out, including the original All For One, causing Japan to descend into chaos. Believing his classmates are no longer be safe, Deku reveals One for All and leaves U.A. to hunt for All For One with Japan's top heroes. However, this leads Deku to physical ruin, and his classmates intervene to bring him back to U.A., which is now a refugee camp. Civilians protest Deku's return until Ochaco pleads to them that heroes need protection too.
After Deku recovers, Class 1-A student Yuga Aoyama is discovered to be a double agent for All For One and the one responsible for the first two League of Villains attacks. After reconciling with his class, the Heroes uses Aoyama's connection to lure the Paranormal Liberation Front into a trap that scatters them across the country for the remaining members to be defeated by the heroes. Toga transforms into Twice using her Quirk with Twice's blood and she nearly kills Ochaco, but the two girls come to an understanding and Toga dies saving Ochaco's life through a fatal blood transfusion. The Todoroki family subdues Dabi after preventing his suicidal final attack. All For One attempts to reach Shigaraki's location but is stalled by many heroes, including All Might using a powered exoskeleton, as well as a handful of reformed Villains. All for One's original body is destroyed by Bakugo, causing Shigaraki to briefly regain control of his body as he battles Deku, before being repossessed. Unable to defeat Shigaraki physically, Deku forcefully transfers One For All during Shigaraki's brief moment of control to damage him from within. Deku, aided by hero reinforcements, strikes the killing blow on both All For One and Shigaraki.
Eight years later, Deku's One For All has completely faded, rendering him Quirkless once again. He is now a hero course teacher at U.A, while his former classmates work as pro heroes or sidekicks. All Might gifts Deku a powered suit that replicates his old quirks, funded by both his former classmates and All Might's old colleagues, which he uses to return to hero work while continuing to teach at U.A. In the following months, Deku enters a relationship with Ochaco and becomes the No. 4 Hero.
