Several years ago, Kaede and her son Shintaro began having a physical relationship, despite knowing it was wrong. However, recently, Shigefumi quit his job and started working from home, and since then they have not been able to have sex, which has increased their desire. One day, Shigefumi goes out for a jog. Shintaro takes this opportunity to ask Kaede for sex. Although he is afraid of the thrill, from that day on, the two of them start having sex during the limited time when his father is away...