One day, the nephew of the husband's parents comes to Tokyo to take his entrance exams. The couple welcomes him, who says he wants to stay at their boarding house in preparation for the exam. Chitose is a kind, caring, busty housewife who is bad at saying no. The virgin student, who is in the prime of his sexual desire, continues to gaze inappropriately at the plump, huge breasts of his "Tokyo aunt". A few days later, on a night when the husband is away at work, the forbidden first sex takes place...!