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 is kidnapped and imprisoned on an isle of prostitutes. To escape, she and Shinpei come up with a plan for her to pose as one herself, but there's one problem. Shinpei forbids her from letting another man touch her, vowing that he will be the only one to protect her. How can Satoko pull off a convincing performance with such a contradictory restriction in place?