In a turbulent era, superheroes emerged, restoring peace to the world. Two brothers, inspired by these legendary figures, pledged to become heroes themselves. Yet, their society classifies individuals as 'Heroes,' guardians of order, and 'Mobs,' tasked with aftermath cleanup. Hiiro, the younger sibling, falls into the 'Mob' category, contrasting with his older brother Ao, who is a 'Hero.' Despite this divide, when their childhood friend Iruka faces peril, Hiiro fearlessly dives into danger, defying the established norms.