Takuo, a college student preparing for entrance exams, is being tutored by Mio, a beautiful woman who moved in next door. Mio, a former teacher, is very good at teaching, and Takuo is looking forward to the time she will teach him. One day, Takuo comes across Mio having an affair. What's more, Mio's lover has taken off her panties and taken them home with him. After that, Mio and Takuo start a closed-door, no-panties lesson...