I made friends with a nice couple that lived in the same building some time ago. We had chats in the corridors and gym and we Became great friends over the years . We were all in our mid 20s , Sean was the guy and his girlfriend Linda was about 5ft 5 inches petit and fit she always wore tight jeans that showed off her nice figure .We would hang out most weekends over a movie and pizza . After a year or so my buddy had to go away to Canada for a few weeks, even when he was away our group chat was very active and Linda would still call me if she was going to get a pizza or chinese and we would hang out After about a month my buddy called me to say that he won't make it back for about 3 -4 months and Linda is really upset and lonely and asked me to keep an eye on her...another month went by and he started joking saying that Linda is frustrated with no sex for 2 months and to be careful around her and I joked back saying that I'd be happy to mind all her needs During all this linda and I became really close and almost were like a couple - calls pizzas movies ... one night while watching a film she put a cushion on my lap and layed down on me and I started rubbing her back ,a few minutes of this and my cock was poking her face throgh the cushion .She looked up and we started making out , it felt right I ripped off her clothes and went down on her .She was wet her nipples hard.We fucked for hours that night and I slept over at her place Sunday morning I left and didn't know what to say or do but she texted that night as usual for pizza and we fucked again and again About 3 months in Sean and I were still chatting ,he was open and telling me about his hook ups over there and reluctantly I said that things happened back here too he was shocked and possibly pissed off for a few minutes but then called me and we had a great chat about how Linda likes to have her Clit rubbed and how she can give great head. It total Sean was away for about 5 months and I had fucoed Linda almost every night tI'll he came back. Linda had a long chat with me about us and how we should still be friends after Sean comes back and we did remain good friends.Wierdly things just went back to the way they were with no awkwardness we were back having our pizza nights and movies One day Sean came over and said that him and Linda had spoken and she had confessed about what happened he said that she claimed that was a one time thing about 3 months in and he had said that he understands and he still wants us all to be friends.The same evening Linda came over and she told.me what she told Sean and asked me if that's OK, I said that it seems we all know what happened and we should move on. For this he next 3 years we were great friends.Linda would come over and we'd have sex when Sean was away on work and I would tell Sean about it and He pretended not to know. Sadly after 3 years they both moved to Canada and ended up getting Married .We are still great friends and we met up when ever they come over. I don't think this was a swinger or cuckold relationship it felt more like two guys being guys and a girl who had needs