When I went to my friend's house to play, I encountered my sister trying to force herself into a pair of pants that didn't fit! I couldn't take my eyes off her erotic appearance as she struggled with her pants completely exposed, and I couldn't help but get an erection! Then she noticed me and tried to hide her ass in a hurry, but she couldn't take off her pants properly, so she asked me for help instead! Every time I helped her, my erect penis hit her body, and my sister got horny...