High school student Taiyou 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, Kyouichirou Yozakura, has been overprotective of her ever since he once rendered her severely injured. His love for Mutsumi is lethal, and Taiyou is his next target. To survive, Taiyou must marry Mutsumi and become a member of the Yozakura family. Thrown headfirst into chaos, Taiyou 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.