Manga Hell's Paradise: Jigokuraku

Gabimaru the Empty, a former ninja killer known as the heartless shell of a man, spends his days on death row wondering when a executioner who is experienced enough to harm him will come, because he does not think about seeing the end of his senseless existence... At least he thought so. Then the mistress executioner, Asaemon the Beheader, revived his hope with a striking proposal. If he ever wants to see his beloved wife again, he must, under the protection of a segunate, go on a dangerous journey to a mysterious mystical island, where the elixir of immortality is said to be located. If he turns out to be one of many rival suicide bombers and scoundrels to find an elixir, he will earn a full excuse and, more importantly, a chance at an ordinary married life with the light of his female life, which made the world seem not so ugly. They are waiting for a trip that does not look like any other!