IENF-095 A high school girl who pitied me, my little sister, agreed to let me 'just rub' and do some dry humping. But we both felt too good, her pussy was soaking wet! Then I slipped in and had raw sex! "What!? It's inside?" But I couldn't stop and ended

My little sister suddenly came to visit my room. She says she doesn't understand her studies, so she teaches, but she gets tired on the way and falls asleep. I got lustful at my sleeping sister and started playing pranks on her sister so that she wouldn't notice, but I was so absorbed in her that I didn't even notice what had happened to her sister! My sister who couldn't see it just rubbed it? and intercrural sex. That should have been the promise...?