Misión: familia Yozakura, 1

Taiyo Asano is a high school student, shyness personified, who can only talk to his childhood friend Mutsumi Yozakura. She, for her part, is the daughter of a family that has been dedicated to espionage for generations and has an older brother whose unhealthy obsession with her has led him to try to eliminate Taiyo. What will he do to protect Mutsumi and himself?!