Hell's Paradise: Jigokuraku #01

Gabimaru the Hollow is one of the most vicious assassins ever to come out of the ninja village of Iwagakure. He's ruthlessly efficient, but a betrayal results in him being handed a death sentence. He has only one hope--in order to earn his freedom, he must travel to a long-hidden island and recover an elixir that will make the shogun immortal. Failure is not an option. On this island, heaven and hell are just a hair's breadth away.--Publisher