When I came in my girlfriends sisters knickers...

My girlfriend still lives at home, but her parents were on holiday so we had the house. She has a younger brother and sister both still teenagers. One night we came to bed and I was feeling incredibly horny as usually, we started playing around as usual and things progressed. Now my girlfriend has an incredible ass, her ass hole is soo tight and I always try and slowly press my finger into her bum but she doesn't have any of it, even though I am dyeing just to push my rock hard dick deep into her tight ass hole. BUT NO. So I tell her to bend over and say "Baby, lets try something..." and slowly start licking her bum, but NO, she doesn't take it and says "Baby just my pussy." So I continue to have sex with her as usual but am just NOT satisfied, so everything finishes and I'm feeling horny as anything still. We come downstairs, she says she's taking the dog out. She leaves the house.

I look outside to see that she's gone and know that NOW is my moment... I go upstairs, walk into my girlfriends sisters bedroom, which is already messy and has stuff everywhere, and on the floor is her beautiful pink knickers. They're crumpled as if they're already worn. They smell as if they are, it's as if I can smell her sweet pussy, as if it's right in front of me. I take out my already rock hard cock and start wanking with her knickers. I cum SO quickly, I clean up my cock head with the knickers and take them home with me.

My girlfriend comes back home, with the dog, makes me a cup of tea, sits back down and we watch TV. Little does she know that I just came in her little sisters underwear and that I wish I was fucking her sweet tight pussy instead of hers.