Amateur cowgirl rides my friend before I see my stepsister

I've been dating this chick for a while now and every time we hang out, it's always a wild ride. This time, she wanted to try riding me in the cowgirl position. I was more than ready to oblige. She wasted no time, straddling me and taking control. Her breasts were bouncing up and down as she rode me, her moans filling the room. I could feel her tight pussy gripping my hard shaft, driving me to the edge. The sight of her riding me was enough to make me explode, but I held back, not wanting to ruin the moment. Just as I was about to cum, my stepsister walked in, catching us in the act. The sight of her reaction only made the orgasm even more intense.