Taiyo Asano is a chronically introverted high school student crippled by grief after losing his family in a horrific car accident. His only emotional anchor is childhood friend Mutsumi Yozakura. However, their quiet dynamic shatters when Taiyo discovers Mutsumi is the head of the legendary Yozakura family, a lineage of elite spies with generations of extraordinary combat skills and dangerous enemies.Complicating matters further is Mutsumi’s fiercely overprotective older brother, Kyoichiro. Traumatized by a past failure that left Mutsumi scarred, Kyoichiro views Taiyo as an intolerable threat and plots his assassination. To save Taiyo's life, Mutsumi proposes a radical solution: marriage. By officially joining the Yozakura family through matrimony, Taiyo gains their absolute
diplomatic immunity, forcing Kyoichiro to spare him.Faced with a terrifying choice between death and marriage, Taiyo chooses survival and commits to protecting Mutsumi himself. Thrust into the clandestine world of espionage, Taiyo undergoes grueling, often life-threatening training by Mutsumi’s eccentric siblings. There is Shion, the brooding hacker; Goliath, the family’s colossal guard dog; Kuso, the chemist; and the chaotic older brothers. Taiyo transforms from a fragile outcast into a resilient combatant, learning lethal techniques, stealth, and weapon mastery.The stakes escalate rapidly as the family becomes targeted by formidable adversaries. Chief among them is Tanpopo, a sinister pharmaceutical organization experimenting on humans to create unstoppable monsters. Led by the enigmatic and ruthless Kawashita, Tanpopo seeks Mutsumi’s unique bloodline for their ultimate genetic synthesis.As Taiyo fights alongside his new family, he uncovers chilling secrets about his own parents' deaths, discovering they were connected to Kawashita’s twisted experiments. This revelation turns the geopolitical struggle into a deeply personal crusade. Taiyo vows to dismantle Tanpopo, protect his bride, and break the tragic
cycle of violence surrounding the Yozakura lineage.Throughout high-stakes rescue missions, infiltrating heavily fortified enemy bases, and confronting psychological trauma, Taiyo and Mutsumi’s fake marriage blossoms into genuine, profound romance. Supported by the unwavering loyalty of the Yozakura siblings, Taiyo embraces his new identity not just as a spy, but as a devoted husband. Together, they wage a relentless war against the shadows, proving that love, trust, and family bonds are the ultimate weapons against darkness.