During the events of the Chushingura incident, Mumyo, a disgruntled Shogunate secret agent, retires from post, disillusioned by the concept of loyalty. Meanwhile, the leader of the Uesugi Clan, who is Lord Kira’s son, sends a group of Ninja assassins to kill the Ako Ronin before they take revenge on his father. But, the chief retainer of the clan sees the foolishness of this plan and hires Mumyo, along with a group of Female Ninja, to stop the assassins and destroy the Ako Ronin from the inside.