So fortunately/unfortunately I'm still not sure, I got caught with my girlfriend's panties, stockings and a sexy mid-length(?) skirt on. I hadn't had time to try on her bra and sweater before getting caught. I was sniffing the sweater's armpits, sometimes my girlfriend seemed to, for one reason or another not worn anti-perspirant/deodorant. Unfortunately she had worn a very feminine smelling deodorant, but there was a faint armpit odor. I was trying to figure out which side had more armpit scent when I got caught. Just to set the tone a little, my girlfriend was a little taller than me in medium heels, and maybe tall as me (6 feet) without shoes, at the time I weighed about 155lbs, she weighed about 120lbs. When she was in her teens and early 20's she was a model for Harley Davidson. So when her sister caught me, it was incredibly akward embarrassing and arousing. She just started laughing. She didn't get the same genes my girlfriend did. She was about 5'4 and 135lbs and dressed like a farm wife. (Because she was?) She sort of laughed and inhaled, staring at me, and being she couldn't exactly leave, her ex-husband dropped her off, I guess she felt we should just be adults about it and talk. She asked if they were her sister's clothes, I said "the t-shirt is mine"... She kind of snorted. "Well I'm surprised you don't have her heels on, her feet are big enough!" She tried to joke. I laughed and said "she has big feet but her shoes don't fit me" I said. Then came the real questions. "Why are you wearing her leather skirt and stockings? "And panties! She added after lifting the skirt high enough to check. I yelled "well it's a good thing, what if I hadnt been?" "I guess I would have seen your bare ass." At this point she was too calm and I was too wound up. "Well?" "Well what? Well why am I wearing xxxxx's panties and skirt? I don't know, I saw the panties, smelled them and put them on and just kept going I guess". "Do you like it?" "I don't know what to say, can I get changed?" I asked. "Go ahead, I'll wait." Came the reply I knew was coming. She always had a crush on me and I knew she was enjoying this. "Can you wait in the living room like a person?" She shook her head and held out her hand. "What?" I thought she wanted to hold hands or something weird. "Panties, give me xxxxx's panties." She said with sass in her voice. I had enough and wanted to get to the bottom of what we were doing. "Why would I give them to you, I got them out of the laundry basket and the skirt was on the bed I capable of putting them back where I got them" I told her. "I'll tell xxxxx you were stretching her leather skirt out, by wearing it!" She won't care, she wears my, never mind.. What do you want Denise?" "Put the sweater on and let me see how you look". "And then we're done, you'll let me change?" "Yep" I grabbed it and put it on, it had stretched out boob spots in the front and was a little snug everywhere else. I turned around and showed her. "Okay, now we're done, let me change, why are you here so early anyway?" "I am without a car so I got dropped off when I could get a ride. Go ahead and change." "Fine." I was not, and am not, the shy type, so I decided I would start stripping and she would get embarrassed and leave. I took off the sweater and my t-shirt rolled up with it. I was pulling my t-shirt back down and I felt her grabbing my cock and grinding against my butt! "Denise what the fuck?" "What? You guys are broke up anyway." I gave in, she was a little cutie in her own way and Ms. Snot wasn't the have sex while you are broken up type anyway. I leaned over and kissed her, she seemed surprised but kissed back. She moved behind me again and pulled up the skirt, and pulled down the panties! She knelt on the floor and started sniffing my ass! "Denise what has gotten in to you?" Xxxxx said your ass always smelled good, well for an ass.." 'You guys talked about our sex life?" "She is my sister" She reached around and grabbed my cock, buried her nose in my cheeks. She started pulling the panties down, and I turned to face her. She grabbed my cheeks and pulled me toward her face, my balls were apparently face height because she started licking them. My cock was stiff against her forehead, she stuck some fingers in my asshole and I nearly spewed semen across the top of her head. I pulled her up but she didn't take her fingers out. "Lay on my lap" she told me. I was confused and horny, asked if she meant the bed or where? She let go of me and sat on the padded chair. "Right here". When I stepped over to her the panties fell around my ankles. She chuckled, and guided me across her lap. I was fully expecting a spanking, instead she went back to anal penetration with probably 3 fingers this time. She asked if I liked it, I said "obviously" which apparently came out snarky because this was to be the first time I got my asshole fisted. No lube, No undue pain, just bliss. I rubbed against her thighs and she just kept fucking my ass with her fist and wrist, in and out, in and out until I spewed hot sticky semen on my legs, her jeans, the leather skirt and the plushy chair. She got up almost as quickly as I did. "We have got to clean this up before Xxxxx gets home!" I agreed and apologized for not reciprocating the orgasm. She said "I got what I wanted". With a smile she took the skirt to the laundry room to clean it. I put my clothes on, tried to clean the semen off the chair, not very successfully, and that was the end of the whole deal. I moved out, Denise never talked to me about the afternoon of embarrassment and semen, and Xxxxx married the guy she had been screwing behind my back... (I think it was a height problem, her new boy toy was 6'7'.). I will never forget it as it was a very weird, very embarrassing, very good afternoon.