Džigokuraku

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? (Crunchyroll)