High school student Taiyô Asano has been socially inept ever since his family died in a car crash. The only person he can properly interact with is his childhood friend, Mutsumi Yozakura, the head of the world's strongest family of spies. Mutsumi's eldest brother, Kyôichirô Yozakura, has been overprotective of her ever since he once rendered her severely injured. His love for Mutsumi is lethal and Taiyô is his next target. To survive, Taiyô must marry Mutsumi and become a member of the Yozakura family. Thrown headfirst into chaos, Taiyô begins his journey to become a powerful spy in order to protect his wife and uncover the dark secrets of his past and the Yozakura family.