My wife's best friend, Sumire, and I have a secret that we can't tell our partners. Since the day we met by chance at a bar, we've been going with the flow and continuing our affair. I care about my wife, but it's a convenient relationship that I can't stop... Our relationship changed completely when we decided to go on a hot spring trip with our respective spouses. I was skeptical when Sumire said we should have sex during the trip, but on the day, Sumire's husband came down with a high fever, so the three of us decided to go on a two-day, one-night trip...