A serious girl of her age, Riena, was troubled because she couldn't keep up with her classmates' sexual topics and couldn't talk to anyone. One day, I visited the teacher's home on a holiday to have my homeroom teacher teach me about sex. However, the teacher is a genuine erotic teacher who goes to customs every Sunday, and was trying to get rid of the troublesome students who visited his home to go to the customs he had reserved, but he was so persistent that he took advantage of her curiosity and toyed with her body in the process of development.