Myself and my partner are on here but have to post anon as she may not like the story. We were out on the town a few of us Friday night, myself girlfriend her sister and some friends. I always had s thing for my partners sister and get along really well. So as the night passes on the drinks start to go to shots and stuff so everybody is getting well on... So I glance at my girlfriends sister beside me her quiet drunk now, my girlfriend sitting the other side of me and a male friend the other side of her, put my arm around my girlfriends sister and bring her in for a mess cuddle.. So as she lays there I could feel her grip getting tighter on my tshirt and body starting to gently caress my chest unknown to her sister (my girlfriend) then she starts to gently kiss my neck disguising her head readying on my shoulder as she does it.. So we decide to go home, our male friend drives, my girlfriend gets into front whilst myself and her sister get in the back. Then they got out to get food but chipper was shut, so as myself and my girlfriends sister sit there for a minute before they get back, my cock pounding out of my pants we look at each other do nothing.. So she leans on my shoulder pretending to go asleep with drunkness but as we leave the lights of the town, she springs to life starts rubbing my chest and kissing my neck again. My girlfriend in deep conversation in the front not aware we cross each other's lips and kiss for about 30 seconds really passionate and good. So take her hand and put it on my already pounding cock and whisper in her ear "careful or your sister will catch us and ruin this on us" I then put my hand on her leg and move up to her pussy teasing her, then start rubbing her tits. So couple of minutes pass and we are home. She starts to act a bit drunk again anyway so the others put her to bed but she won't get in proper so I head in and lift her in and whilst doing it she starts kissing my neck again and I put her down. All this happened whilst the others never noticed, I think she was putting the drunkness on but just wanted to have me so bad as she loves the daredevil approach unlike my girlfriend. So the question is where to now? Anybody got advice. I'd love to bend her over and force my cock into her tight little pussy and ass. But do I run the risk of her telling my girlfriend, or do I just sit it out and nothing happen. I don't think my girlfriend ever envisaged swinging like this but god it's such a turn on what happened! Advice advice advice????