Koichi Haimawari dreams of being a hero, but writes off his sliding Quirk as too weak for a license. Instead he patrols the streets doing small good deeds, picking up trash and helping lost kids. After thugs jump him and the street idol Kazuho Haneyama, the brutal masked vigilante Knuckleduster steps in and pulls them both into unlicensed crime-fighting. Set five years before the main series, their work on the city's underside keeps them dodging the police and the pro heroes who treat their help as a crime.