A young man returns to Tokyo after a long absence and pays a visit to his relatives, including his mother's younger sister, Yoshimi Miyazaki. Seeing her again after so many years, he becomes acutely aware of her mature, alluring figure. Having always looked up to her like a mother since childhood, the more time he spends with her, the more his feelings begin to shift. On the day he decides to become independent—securing a new job and apartment—he finds himself alone with his aunt. Unable to suppress his emotions any longer, he crosses the boundary between aunt and nephew, giving rise to a forbidden, intimate relationship.