Afflicted with a heart condition, Meiji-era noblewoman Satoko is determined to secure a marriage that will benefit her family before she dies. But before she can realize her goal, she's targeted by a mysterious assassin named Shinpei. In a last-ditch effort to save her life, Satoko asks her would-be murderer to marry her. Her proposal isn't sincere, but unfortunately for her, Shinpei loves as intensely as he kills. Can Satoko find a way to break the engagement without losing her life?

Satoko and her allies hatch a daring plan to drive out Asagiri's tormentors--disguise Shinpei as a prostitute and send him straight into the enemy's den! Eager for Satoko's praise, Shinpei throws himself into battle and cuts down his foes with bloodthirsty enthusiasm. But as the plan unfolds, a far more serious resolve begins to take root in Satoko's heart.