The wife seduces her brother-in-law right at the parents' house

This is not the first time I have been to my mother-in-law's house, but I still feel extremely nervous. Coincidentally, my sister-in-law and her husband also came to visit. While going to the toilet, I accidentally saw my sister-in-law naked, she was truly beautiful, her seductive body made me unable to think straight. The next day, when everyone went out and only my sister-in-law and I were at home, she seduced me.

Although I knew this was wrong, I couldn't resist her allure. We had sex when everyone was away, and even when my wife was sleeping next to us...