Set during the Edo period, the story follows Gabimaru the Hollow, a legendary and seemingly emotionless ninja from Iwagakure sentenced to death for his betrayal. However, every execution method fails due to his superhuman body and hardened resolve. Intrigued, the eccentric executioner Sagiri Yamada Asaemon recognizes that Gabimaru secretly clings to a deep desire to live, driven entirely by his fierce love for his devoted wife. Sagiri offers him a pardon from the Shogun under one condition: he must travel to Shinsenkyo, a mysterious and lethal island rumored to be the Buddhist pure land, to retrieve the
Elixir of Life.Gabimaru accepts, joining a deadly expedition alongside other violent death row inmates and their assigned Asaemon executioners. Upon arriving, the group quickly discovers that Shinsenkyo is far from paradise. The island is a grotesque, beautiful nightmare teeming with bizarre, monstrous flora and fauna, alongside immortal, god-like beings known as the Tensen. These rulers protect the elixir and ruthlessly slaughter intruders by manipulating Qi, the fundamental life energy of the universe.As the mission devolves into a desperate
fight for survival, shifting alliances form among the cutthroat criminals and the honor-bound executioners. Gabimaru forms a fragile partnership with Sagiri, who struggles with her own inner turmoil regarding taking human life and proving her worth as a female executioner. Through brutal battles against the Tensen, Gabimaru learns to harness Qi, unlocking terrifying new levels of his ninja abilities. However, using this power chips away at his humanity, transforming him back into the unfeeling monster he once was and threatening to erase the memories of his wife.Simultaneously, other inmates and executioners uncover the horrifying truth behind the island: the Tensen are harvesting human lives to manufacture the elixir, and the Shogun's expedition was merely a sacrificial scouting mission. Betrayals mount and casualties rise as different factions race to survive the island's relentless onslaught. Gabimaru and Sagiri must bridge the gap between their opposing worlds, fighting not just for a imperial pardon, but for the preservation of their own souls. Ultimately, the survivors realize that escaping Shinsenkyo will require facing the supreme rulers of the island in a cataclysmic final showdown that will test the limits of human endurance, morality, and the enduring power of love against seemingly insurmountable, divine evil.