Kotone, a normally serious girl, was secretly worried that she couldn't keep up with her classmates' conversations about sex. One day, she decided to go to her PE teacher's house on a weekend to ask him to teach her about sex. However, the teacher was a genuine lustful teacher who visited a brothel every week. At first, he tried to get rid of Kotone, who had come to his house to go to the brothel, but he took advantage of her troubles and gradually started playing with her body. Kotone also took what the teacher said seriously, and gradually he took control of her body and Kokoro...