A nephew temporarily staying at his aunt's house to focus on his upcoming college entrance exams finds it hard to concentrate. Though she encourages him with a cheerful "Good luck on your exam!", he's surprised by how beautiful she is, with an exceptional figure—especially her large, voluptuous breasts, which begin to stir his emotions. Living in close quarters with her makes studying increasingly difficult, and one day, he accidentally catches her masturbating in the living room. From that moment on, his feelings change completely.