I have a secret that I can not tell my wife's best friend Sumire and each other's partners. Since the day we met by chance at a certain bar, we have continued to have an affair. My wife is important, but it's a convenient relationship that can't be stopped. The relationship changed completely when it was decided to go on a hot spring trip with each other's couple. I was skeptical when I heard about Sumire saying that we should have sex during the trip, but on the day Sumire's husband got a high fever, and the three of us decided to go on a two-day, one-night trip.