What was always in front of me was a black butt... - I live with my girlfriend and her sister. - My younger sister is a gal and doesn't wear skirts at home and always wears a thong. - Don't you think of me as a man? - I can't stay rational when my sister walks around the house with her black butt sticking out... - When I got fully erect, I moved my thong and inserted it all in from behind. - I lost my mind and forgot to put on the elastic and kept shaking my hips until I cum inside her.