Set in feudal Japan, the narrative follows Jubei Kibagami, a wandering, cynical swordsman haunted by a violent past. While traveling through a war-torn province, Jubei rescues a courageous Koga ninja named Kagero from the vicious giant Mushizo, who belongs to the Devils of Domon. This rogue faction of eight supernatural ninja warriors serves an enigmatic mastermind known as Himuro Gemma. Kagero possesses deadly skin that is poisonous to the touch, a curse bestowed upon her by her clan to serve as an ultimate weapon. Their fateful encounter draws Jubei into a treacherous web of
political conspiracy and dark sorcery.Soon, Jubei and Kagero are joined by Shigure, a clever government spy posing as a blind priest. Shigure recognizes Jubei and enlists his aid to uncover why an entire village has been mysteriously wiped out by a lethal plague. As they journey deeper into the domain, they are relentlessly hunted by the remaining Devils of Domon. Each assassin wields terrifying, unnatural abilities, forcing Jubei into brutal, life-or-death battles. He faces opponents like Tessai, a brute who can turn his skin to stone, and Benisato, a seductress who commands
venomous snakes. Despite his desire to remain a neutral mercenary, Jubei’s sense of honor and his growing attachment to Kagero compel him to stand and fight.The plot thickens when it is revealed that the true architect of the chaos is Himuro Gemma, a legendary ninja warlord whom Jubei supposedly killed years ago. Gemma has returned through dark arts, seeking immortality and the gold mine of the nearby Toyotomi clan. To achieve his ultimate goal, Gemma requires Kagero’s unique blood to complete an elixir that will grant him eternal life and invulnerability.Tragedy strikes when Kagero is captured and subjected to Gemma's cruel manipulations, culminating in her tragic death despite Jubei’s desperate rescue attempt. Enraged and grief-stricken, Jubei confronts Gemma in a cataclysmic final showdown amidst a collapsing, fire-engulfed fortress. Utilizing his supreme swordsmanship, Jubei outsmarts Gemma's regenerative powers by exploiting a fatal weakness in his immortal anatomy, finally defeating his immortal nemesis once and for all.With Gemma destroyed and the conspiracy thwarted, the surviving gold is secured, and peace briefly returns to the scarred landscape. Rejecting rewards and government service, Jubei declines Shigure’s offer to stay, choosing instead to return to his solitary life on the road. As he walks off into the horizon, Jubei carries the bittersweet memory of Kagero, cementing his status as a legendary, wandering warrior who forever remains detached from the world he protects.