I was planning to go to Tokyo to watch a concert, but the hotel was fully booked, so I had to stay at my sister's house. On the first night of my stay, I accidentally saw my sister and her husband having intense sex, and my sexless body couldn't help but indulge in masturbation. Unaware that my brother-in-law was watching me. The next day, as soon as my sister went out for work, my brother-in-law approached me. Even though I knew it was wrong, my sexless body was overwhelmed by his incredible stamina.