I'm not much of a story teller, but I'll try.
My gf doesn't live with me, she still lives with her parents and sister (she is 20, sister is 23, I'm 24). They are Filipina and the sisters look almost identical though my gf is slightly taller and her sister is bustier. Both are really pretty and I've always found her sister attractive but I've obviously kept that to myself. Sometimes I catch her looking at me when I'm over at their place and we smile at each other, and I've often thought that I could have ended up with her sister just as easily, except I probably never would have met her otherwise (my gf and I are in the same program, and her sister works and doesn't go to school).
Anyway we got her sister a 3 month gym membership for Christmas and she texted me last weekend to thank me, and she mentioned that she was super sore from her first workout in a while. We don't usually communicate at all but we texted a couple of times around Christmas about gifts for my gf and whatnot. Nothing scandalous. Anyway, something about her text really turned me on, so I sent her a wink back and told her to take it easy on herself, not to leave any marks, and she texted back saying she doesn't mind a few bruises. It sort of went from there... we chatted back and forth for a while, nothing sexual mind you, but it seemed flirty and dangerous, lots of innuendo. We literally texted back and forth until 2am.
Anyway, yesterday afternoon she texted me and asked me if I was home because she was downtown and had some time to kill before the next train (they live in the suburbs), so I said I was home and invited her over to watch tv. She had never been to my place before, so it was weird, and I wasn't sure what to expect, but I quickly showered and got ready just in case. From the look on her face when she showed up it was clear something was going to happen. There wasn't much pretense, she came in, looked around, then we started kissing even before we could sit down and pretend to watch TV. She just sort of stepped to me, into my personal space, and smiled up at me. Once we started kissing, everything went quickly and naturally. We spent the whole afternoon fucking each other, and she left around 7pm. Quite literally, it was the best sex I've ever had.
I haven't spoken to my gf yet, we just texted back and forth a few times but I told her I'm not feeling well and just sleeping and watching netflix. Not sure what the hell is going to happen now.