A couple years ago I was friends with a girl who was also pretty slutty. A large part of our friendship was talking to each other about sex, what we were into, recent fucks, what we didn’t like in bed etc. She was in a long term, but open, relationship with a guy. They’d agreed between them that fucking other people was ok, and it seemed like it was working out well for them.
At some point her bf and I were chatting and he mentioned that she never let him fuck her ass. I knew their relationship was open so I (mostly jokingly) offered to him that if he ever really wanted to take some girl’s ass he should hmu and I’d do it.
A couple weeks later I got a text from him asking if I was free and could he come over. I said sure, and about half an hour later he was sitting in my kitchen with me. We briefly exchanged smalltalk and then he asked me if I’d been serious about my comment before about how I’d let him fuck me.