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

Taiyo Asano has been on his own ever since his parents died. 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!

Ever since the addition of the newest members of the Yozakura family, the twins Hifumi and Alpha, it's been nonstop chaos. Upon meeting their Aunt Futaba, Alpha is instantly smitten...which makes Hifumi, who's unnaturally attached to her brother, jealous enough to foolishly challenge Futaba to a battle. Then Shion and Kengo, both five years older now, return to meet their new niece and nephew!