Natsuko, my mother's best friend from her school days, came to stay with the Sato family. - Her son Satoru is drawn into Natsuko's adult charm. - When Natsuko learns that Satoru is still a virgin, she gently instructs him, saying, ``I'll be your first woman.'' - Nervous and confused, Satoru successfully loses his virginity and wants Natsuko again and again like a newly learned monkey...