Hell's Paradise: Jigokuraku

Gabimaru the Hollow, a ninja of Iwagakure Village known for being cold and emotionless, was set up by his fellow ninja and is now on death row. However, no method of execution works for him. Asaemon the Decapitator sees this and has a proposal for the ninja. She wants Gabimaru to join an expedition to an island south of Japan in search of the elixir of life in exchange for a full pardon by the Shogunate. However, this island isn't a normal island: it's believed to be Paradise.