One night and two days of 1 night and left alone by my wife's sister who suddenly came over

While my wife was on a two-day trip with a friend, her husband Shota was in trouble with the messy living room. Just as I was thinking about cleaning it soon, my wife's sister Momoba came to help out with the housework. Shota was grateful to Momoha for being responsible for all the housework, but Momoha's true purpose was to resolve his frustration with Shota. Without realizing that, I was taking a bath and was so enthusiastic about it that Momoba came over...