Through the caregiving, the young girl and the elderly man become aware of each other as a man and a woman, and even develop a physical relationship. A female college student volunteering as a caregiver in preparation for her future career and community service is put in charge of an elderly man who has lost his wife and lives alone, and is often sick. Although he thinks of the devoted and kind girl as a granddaughter, the elderly man, whose lower body is energetic, cannot suppress his sexual desire at the sight of the girl's voluptuous, full breasts, so he takes his penis out of his diaper and masturbates with the girl's apron. However, the girl, who has seen the act, is flustered by the old man's erect penis. Thinking that caring for his private parts is also part of the caregiving, she serves him. From then on, like a kite with a broken string, the two cross the line.