background At first it was great. We were roommates: we met on a fb group of our university for flat sharing and we ended up living together. For the purpose of this story I'll call her "Alex". We were four in our flat: me, Alex and a couple. As the others (the couple) were never home and often went back to their hometown for weekends, I and Alex started to know each other. We had two single rooms and always found excuses to get in the same room together "I can't study in mine, is too hot/ cold", "wanna help me cooking" etc. We weren't ready for a relationship at the time (I didn't want a relationship at all, while she was just out of a 5-years one) but it was clear we liked each other.
getting started So as we both liked each other there have been a few situations at first: one night we were a bit drunk and kissed. After that, in the following weeks we kissed a few more times and started trying to figure out what we wanted. I liked her, she liked me, but for the above reasons, we decided to just be friends with benefits. It was the first time trying this for both of us. So following our decision we tried to have sex, which was 'meh' the first time. We both were nervous as apparently, we hadn't clear what we were as a couple, if that makes sense. We were shy and trying to impress the other, somehow.
the good part So we just decided to be honest and 'use' each other for pleasure. This was the best part. In a week or so we managed to act naturally and our routine worked pretty well: our life was that of two single individuals who shared a flat and we're friends. However, when the other couple wasn't home (I don't know why we did this only when they weren't home) we started to tell the other what we liked. And this, was the best sex I ever had. We could be 100% honest. I could ask her for a blowjob whenever I wanted. She used to ask me for a lot of oral sex too. The best part is, we used to give instructions so that the other person could make a better job. This was mostly 1-sided which means we hardly had sex, but rather have her getting me off or vice versa. That could also have been through proper sex, although we used to have one person giving instructions and the other following them. E.g. I often asked her to ride me in a cow girl position in the morning and she used to ask me to fuck her doggy style while she watched porn. Anyway, it was good, maybe too good. We started to want more and more sex. A normal day could have easily gone like this: I wake up, go to her room, we fuck. We take a shower together and I give her oral sex. We have breakfast while watching the news, and she gives me a footjob / handjob before I go out or while I finish watching the news. When we come back home for dinner, we'd have the most kinky sex and eventually take another shower. If the other couple is not home, we would also play in their room like dressing Alex with the other girl's lingerie or using their toys.
It didn't work anymore. We were kind of sex-addicted which wasn't bad per se, but we had no interest in each other apart for physical attraction.
bad part We were both attractive hence we used to see other persons quite often. One night we both had a date and ended up asking our partners to have a orgy which they both refused. We realised t was time to move on with our sentimental lives and get shit done