A young boy named Jiro discovers that his mother and sister have been murdered in his home. Wrongfully accused of the crime, he flees his village and encounters a priest named Tenkai, who tasks him with killing a rogue ninja named Tarouza. After completing this assignment, Jiro is trained to become a master assassin. Years later, he learns that he is actually the son of Tarouza, who had once worked for Tenkai but abandoned his mission after falling in love with an Ainu woman. Jiro also uncovers that the Shogunate plans to recover the lost treasure of Captain Kidd and use it to isolate Japan once again. Guided by the clues Tarouza had hidden, Jiro, along with the female ninja Oyuki and a...