After vanquishing Boros and his forces, Saitama resumes his mundane routine in Z-City. Unbeknownst to him, the monster population surges, straining the Hero Association. Resorting to an unconventional tactic, they recruit thugs to aid their cause. Amidst this, a sinister figure named Garou emerges, declaring himself a monster and launching vicious assaults. Garou, once Silverfang's prized pupil, remains an enigma with a destructive path. Enticed by the chaos and driven by greed, Saitama enters a martial arts contest where Garou runs amok. As the tournament unfolds and Garou poses a dire threat, a new peril emerges, echoing the prophetic warnings of Madame Shibabawa. Is this the cataclysm she foretold, looming over humanity?