It's the 25th year since Shigeo and Yuko got married, their "silver wedding anniversary." To celebrate, the group goes on a trip to a hot spring, planned by Shigeo's daughter, Kiriko, and her fiance, Yuji. Since Kiriko has grown up, there hasn't been a chance for the family to go out together, so Yuko enjoys chatting with Kiriko while soaking in the open-air bath with a spectacular view. However, there is a man staring at Yuko with a gaze that seems to lick her up. Then, that night, while Shigeo and Kiriko are drunk and not looking, Yuji makes a certain move...