Romance! A crazy, overprotective brother! And...spies?!

Taiyo Asano has been on his own ever since his parents died and the only one who seems to care for him is his childhood friend and classmate, Mutsumi Yozakura. But Mutsumi has a secret–she is the head of a family of spies! And on top of that, her brother Kyoichiro is dangerously protective of her! To stop Kyoichiro from killing him, Taiyo and Mutsumi must take the ultimate leap–marriage! Because in the Yozakura family, family cannot kill family.

The family receives a shock when Kyoichiro goes off on his own, leaving a mysterious note that says not to look for him! Convinced he really ran away, the family uses all their sophisticated spy powers to track him down. But Kyoichiro had a reason to leave—he faces a ghost from the past that could destroy the entire family!