I discovered my stepsister having sex with her boyfriend and threatened to tell our mom if she didn't have sex with me

In a shocking turn of events, I stumbled upon my 18-year-old stepsister getting intimate with her boyfriend. I was taken aback by the sight, but I knew I had to seize the opportunity. I confronted her and made a bold demand - I wanted a taste of the action too. With a mix of fear and desperation, she agreed to my proposal. The thought of revealing our secret to our mom was enough to ensure her compliance. I wasted no time, unzipping my pants to reveal my throbbing member. She hesitated for a moment, but then she took me in, her eyes filled with a mix of fear and desire. The sight of her big, natural tits bouncing as she rode me was enough to drive me wild. I took her in various positions, each one more intense than the last. The thought of her boyfriend walking in only added to the excitement, making the experience even more thrilling. In the end, we both got what we wanted, and we left the room with a silent understanding between us.