Immediately after his sudden turn of events, his mother remarried and he suddenly had to live with his stepfather and sister-in-law. My older sister Mai was stunned when she saw me for the first time. ``I never heard that he was going to have a younger brother. I thought he would be around the age of a student.'' Maybe he was worried about living with such a big brother. I felt a little sorry. However, after a week had passed, perhaps because we were living together, my sister started wandering around the house wearing a housecoat that looked like underwear and had her big butt sticking out. "Don't stare at me. I'm at home, so it doesn't matter how I dress, right?" No, no, I can't stand it if you dress so erotically! I was defenseless and suddenly got an erection in my ass, so I hurried back to my room and masturbated. My naughty older sister, who knows about my sexual situation, shows off her erotic ass every day. My sister was napping on the sofa in the living room with her butt exposed...I accidentally touched her big butt...it was so soft...I thought it would become a dangerous habit...I was massaging it in a frenzy when my sister woke up. It happened. "Hey, what are you doing? Stop...we're sister and brother, aren't we?" I know that...but my rationality is gone...I'm sorry, Mom! But I can't back down anymore! ! I bury my face in the soft ass meat, rub my crotch against the crack of the ass, and insert it completely from behind... It's crazy... I can't stand the feeling of this ass rippling... It feels so good, I piston it hard! Without thinking about what happened, I injected a thick layer of semen deep into my sister's vagina... I did it... Incest... The family was destroyed... The next day, my sister was calm. I didn't feel bad for my parents...Maybe they didn't like me? I got carried away and started chasing my sister's butt around, stealth from my parents' eyes...