Turns out there were actually 3 of his friends there and they all looked pretty good. I sat on the couch and started talking to his friends and before...long one of them was rubbing my leg. I had on a denim skirt and the inside of my upper legs are very sensitive. As we all talked he kept rubbing my leg and soon his hand wandered up under my skirt.My friend came up behind the couch, leaned over and started nibbling on my neck...again another very sensitive part of my body. One of the other guys. You let go off your buttocks and you grip the table and I am now fully in your asshole. Your ass cheeks are pressed up against my crotch and I love the feeling of having your ass against me like this, even though your skin is damp from sweat from the workout but it just greatly improves the feeling of your skin against mine.At first I gently start thrusting and tenderly caressing your asshole with my cock, which you love and you let me know by groaning quietly and smiling at me over your. I finally had an excuse to get up and I was even happier to see her turn off the light. As I began to stand up I realized that my towel was not coming with me. By the time I stood up I was completely naked, facing away from my sister. My body blushed and I knew I was screwed. I looked back to see her trying to look at my cock. I felt it grow even more.She handed me the towel but never looked away. I began to wrap it around me as I heard her whisper, "Leave it off."My mind was racing; my heart. "Is that what you've come here to get? Only 'services'?" I asked her.She smiled back to me and said not necessarily. She wouldn't say no to a true love if she met it, but as the likelihood of that wasn't too great, 'services' might be nice for the time being.After that, it was easy to turn the conversation to our specific preferences. I had never told anyone about my deepest desires to anyone, but telling them to her was easy, so natural that they just came out as a perfectly natural part of.