Marina, a teenage girl, was secretly worried because she couldn't keep up with her classmates' erotic conversations. One day, she decided to go to her homeroom teacher's house on a holiday to ask him to teach her about sex. However, her homeroom teacher was a genuine lustful teacher who visited a brothel every week. At first, Marina came to his house to go to a brothel she had reserved, and he tried to get rid of her, but she was so persistent that he took advantage of her Kokoro and started to play with her body, which was still in the process of development. Marina also took his teacher's words seriously, and gradually he began to control her...