After my older brother got married, I ended up living with them as a housemate. My life with Kanna began, and while she was kind, skilled at housework, and had a wonderful personality, she was oblivious to fashion. Seeing her doing chores in just a thong and tank top made my teenage heart race. One day, I was caught by surprise holding my sister-in-law's underwear, and in that moment, my rationality vanished—I immediately plunged deep into her thong-covered ass. I kept thrusting into her relentlessly until her anus twitched and spasmed uncontrollably. I ended up giving my forbidden sister-in-law multiple creampie orgasms, even though I knew I should never have touched her.