A young boy named Jiro discovers that his mother and sister have been murdered in his home. Wrongly accused of the crime, he escapes his village and encounters a priest named Tenkai, who orders him to kill a rogue ninja named Tarouza. After completing this task, Jiro undergoes training to become a master assassin. Many years later, Jiro learns that he was an orphan and that his biological father was Tarouza, who had worked for Tenkai until he abandoned his mission upon falling in love with an Ainu woman. The young ninja uncovers the fact that the Shogunate intended to retrieve Captain Kidd's lost treasure and use it to once again isolate Japan from the rest of the world. Using the clues that Tarouza had kept secret, Jiro—along with the female ninja Oyuki and a slave named Sam—travels to Russia and America to search for the treasure, hoping to use it to exact revenge on Tenkai.