Ever since Taiyou Asano lost his family in a tragic car accident, he's struggled with social interactions. The only person he feels comfortable with is his childhood friend, Mutsumi Yozakura, who happens to lead the world's most powerful family of spies.
However, Mutsumi's brother Kyouichirou, fiercely protective due to a past incident that left Mutsumi injured, views Taiyou as a threat. In a bid to survive, Taiyou agrees to marry Mutsumi and join the Yozakura clan. Plunged into a world of espionage and danger, Taiyou must navigate treacherous waters to safeguard his wife and unearth the secrets that haunt both his past and the Yozakura family.