Shiro is a complete mother's boy and went on to college within the range where he could commute from home. In addition, his sexual interest only comes to his mother, Rie. Rie, who is in her maturity, thinks that she wants to have a sexual relationship with Shiro rather than her husband who is in a sexless state. Today, Rie and Shiro are going on a hot spring trip together. Rie was a little worried that she might end up marrying Shiro on this trip...
