Gabimaru reigns as the strongest and most ruthless assassin in his village. But now finds himself on death row—with only one way out: retrieve the Elixir of Life from a sinister island. Longing for freedom, he accepts the challenge. But with fellow convicts vying for the same prize and demonic beasts lurking, how will Gabimaru survive this harrowing quest?

Denji has a simple dream—to live a happy and peaceful life, spending time with a girl he likes. This is a far cry from reality, however, as Denji is forced by the yakuza into killing devils in order to pay off his crushing debts. Using his pet devil Pochita as a weapon, he is ready to do anything for a bit of cash.