Yuri, his mother's best friend, who ran away from home after a fight due to her husband's infidelity, is staying at their house for a while. Satoshi is excited by her sex appeal and sexy body, which is hard to believe for a classmate of his mother's, and his Kokoro is pounding... Unable to suppress his curiosity about Yuri, Satoshi peeks at her naked body while she is changing in the bathroom. When Satoshi returns to his room, he can't help but masturbate to Yuri's voluptuous body, but Yuri sees him masturbating instead...