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 Yozakura siblings show up at Shinzo's wedding ceremony fully ready to crash it! But Ryu's clever plot quickly saps them of their will to fight. Only Taiyo and the twins are left standing, but thanks to the twins' efforts, Ryu shows his true colors. Then it's down to a one-on-one between him and Taiyo!.