Chisato is invited by her only daughter Mizuki and her husband to a hot spring resort. It's been a while since Chisato's last time, and she's relaxing in the open-air bath, but her everyday fatigue has taken over and she ends up overheating in the bath. Mizuki's husband, Kenji, is the one to help her out. Kenji carries Chisato's ripe body to the room. That night... Kenji can't forget the feeling of Chisato's body from earlier. He takes advantage of the opportunity when everyone is drunk and makes a move on Chisato, but...