Natsuko, my mother's best friend since I was a student, came to stay at the Sato family. His son, Satoru, is drawn to Natsuko's charm, which is full of adult charm. When she learns that Satoru is still a virgin, Natsuko gently teaches, "I will be the first woman." Satoru, who graduated from virginity brilliantly while being nervous and confused, wants Natsuko many times like a monkey he has just learned.