Hyoudo Riki is a perfectly normal teen -- until his evil twin from an alternate world takes partial possession of him. Soon Hyoudo is at the mercy of the masters of the Dark Realm, who would like to take over our universe. They begin their dirty work with Hyoudo's schoolmates, whom they transform into a gang of horrible sex-obsessed creatures.

Nor will the nastiness end there, because some other onlookers are eager to enter the fray. The only possibility for salvation is the heroic Zankan, a Space-Time policeman who might be able to put everything in its proper place once again.