A dying noblewoman proposes to the assassin sent to kill her, and somehow that becomes the most honest conversation about love either of them has ever had. Shinpei doesn't fall for her because she's beautiful or desperate; he falls because she's already bargaining with death, which means she stops lying about what she actually wants. By the time you realize this is a love story about two people who have nothing left to lose, it's already too late to protect yourself from it.

Satoko, eldest daughter of the noble Kirigaya family, is admired for her beauty and grace and hopes a good marriage will prove her worth to her relatives and ease her father's worries. She hides a heart condition that leaves her little time to live. While out on a walk, she is seized by mercenaries, among them Shinpei Gotou, a legendary assassin sent to execute her. When bribery fails, Satoko claims love at first sight and asks him to marry her. To her surprise, he agrees and swears to protect her. As the two flee together, she struggles to keep up the act and to understand the enigmatic man at her side, who treats the idea of being bound until death with complete seriousness.