Takashi's father, unable to bear the sight of Takashi's inability to study, asks his colleague's wife, Riho, to be his tutor, but Takashi can't concentrate on his studies because he is distracted by the beautiful tutor Riho's breasts. Riho is embarrassed by Takashi's Ke'ai and vigor, but she takes off her bra... Inspired by the young boy's naked sexual desire, Riho's private lessons develop into an erotic one...!