Step sister discovers her step brother's arousal after sensual self-pleasure

After a relaxing massage, my step sister decided to please herself by sensually rubbing her pussy. I was in the same room and couldn't help but notice her arousal. She seemed to be enjoying herself, moaning softly as she continued to pleasure herself. I couldn't resist and decided to join in on her fun. I moved closer to her and began to touch her, exploring her body and making her moan even louder. It wasn't long before I was fully engaged in fucking her, my cock sliding in and out of her tight pussy. The sensation was intense, and I could feel her body responding to my every move. As I continued to fuck her, I could feel myself getting closer and closer to the edge, my body trembling with anticipation. And then, with a final thrust, I came all over her big ass, my body shuddering with pleasure as I watched her smile at my reaction.