The father, worried about his son's poor academic performance, asks Nana, his friend's wife, to become a private tutor. However, the son becomes completely distracted by Nana's large breasts, forgetting all about studying and even the lessons themselves. Concerned, Nana tries even harder to improve his grades, but her teaching methods are highly erotic, drawing the son in even more. As a result, the tutoring sessions become far more lewd than expected, and the relationship between the two grows increasingly intimate.