My wife and I went back to my wife's parents' house for the first time in a long time. We were having a pleasant conversation with my parents-in-law, but my wife left the table after she said that she wanted to see my father-in-law's grandchild. I tried to flatter my parents-in-law, but finally I told them that we hadn't had sex tonight. I woke up in the middle of the night and happened to witness my parents-in-law having sex. However, my father-in-law had lost his erection and my mother-in-law didn't seem satisfied. Excited, I hurried to the dressing room. There, I found my mother-in-law's underwear and masturbated enthusiastically...