In a sword-and-sorcery world, the dreaded necromancer known as the Corpse God is cornered by the hero Shagrua Edith Lugrid. Rather than die, he casts a reincarnation spell and wakes in modern Shinjuku, inside the body of Polka Shinoyama, a boy whose throat was just cut by an assassin. Seeing in this city the peaceful life he never had, the necromancer keeps Polka's name and begins feeling his way through Shinjuku's criminal underworld.