It was supposed to be just dry humping, but it turned into a serious insertion! I was so annoying that my sister, who was worried about me as she was about to drop out of school, came to my room over and over again, so I half-jokingly said, "If you let me do it, I'll listen to what I'm saying," and I agreed that it was just a dry humping! However, my sister's pussy, which was rubbed against her crotch, accepted my dick and turned into incest!