A superhero-loving boy without any powers is determined to enroll in a prestigious hero academy and learn what it really means to be a hero. The film set after the term-end examination ended. While the members of U.A. High School are waiting for a forest camp in the summer vacation, DEKU and All Might are visiting I Island, a moving city with huge population that floats on a foreign sea, with an invitation from someone. Deku meets a girl named Melissa who has no "Quirk." She reminds Deku of himself in the past who also lacked a "Quirk." All of sudden, the security system of the island is hacked by an unknown villain and all of the people in the island are being held hostage. Then "a project" that may shock the structure of the hero society is launched. The one person who holds the key to the project is All Might, the symbol of peace.
