I went out drinking with some friends and afterwards my guy friend needed a place to crash because he didn't want to drive home. We talked on the couch for a bit and he mentioned that he was super horny. I didn't really want to fuck him because I had a boyfriend at the time so I told him that if he wanted to, he could use me as inspiration and jerk off. No touching though. He seemed excited. He asked me to lay face down on the couch with my knees on the floor and pull my skirt up so I did. I was wearing a black lace thong that my asshole peaked just barely out of the sides of. He positioned himself behind me and started jacking off. I didn't want him to take forever so I pulled my thong down and shook my butt side to side. I could tell he was getting close so right before he came I told him "cum on me" and I spread my ass apart with my hands so he could see everything nice and clear. He let out an audible grunt as he put a hot load all over me, including on my asshole. I cleaned up, handed him a pillow and blanket for the couch and went to bed.