The protagonist is a monstrous antihero, a result of falling into a vat of toxic waste, and has become the defender of Tromaville, a town once plagued by corruption and crime. Now a hero to the community, he lives a relatively peaceful life alongside his blind girlfriend. However, the serenity is shattered when an evil corporation, Apocalypse Inc., arrives with a nefarious plan to turn Tromaville into a wasteland of pollution and despair. The corporation's chairman sends goons to eliminate the hero, fearing that his presence could foil their dastardly scheme. After a series of altercations, the chairman realizes that to defeat the mutant crusader, he needs to uncover his human weaknesses.

In search of answers, the chairman discovers the protagonist's father's whereabouts and devises a plot to lure the hero out of town. The hero embarks on a journey to Japan under the false impression that his father is in danger and that his origins can be traced back there. He faces multiple challenges overseas, including cultural shocks and battling a different array of evildoers. Meanwhile, back in Tromaville, the corporation implements its toxic takeover, exploiting the hero's absence. His girlfriend, despondent over his departure, attempts to cope with the looming disaster while harboring the hope for his triumphant return.