Hell's Paradise Jigokuraku Vol 1

Even an invincible ninja may not be able to survive Hell's Paradise!
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.