A serious girl for her age, Riena, got into trouble because she couldn't keep up with her classmates' sexual topics and couldn't talk to anyone. One day, I went to the teacher’s house on a day off to have my homeroom teacher teach me about sex. However, the teacher was a real perverted teacher, going to customs every Sunday, and trying to get rid of troublesome students visiting his house to go to the customs he had arranged, but he was too stubborn and exploited her curiosity, teasing her developing body.