In a grim, post-apocalyptic megacity known only as "The Hole," sorcerers from another dimension treat the human inhabitants as guinea pigs for their magical experiments. Caiman is one such victim—a man with the head of a lizard and a total lack of memories regarding his past. Immune to magic and possessing a mysterious second head inside his throat, Caiman spends his days hunting sorcerers with his best friend Nikaido, biting their heads to let the "man inside" identify his attacker. Their quest for the truth sparks a bloody, chaotic war between the residents of the Hole and the powerful "En Family" of sorcerers, all while everyone just wants to find a good place to eat gyoza.