My wife’s best friend Sumire and I share a secret neither of us can tell our partners. Ever since a chance meeting at a bar, we have drifted into an ongoing affair. I love my wife, but our convenient relationship is impossible to quit. Everything changed when both couples planned a hot-spring trip together. I barely believed Sumire when she said we would have sex during the trip, but on departure day her husband came down with a high fever, leaving just Sumire, my wife, and me to take the overnight trip.