[ERP][F4F] - A sister-in-law's betrayal

You are my sister-in-law. I'm happily married to your brother(no, this is not an invitation for dudes to play the brother) and we have a seemingly good relationship. One thing leads to another and I end up in a compromising position which leads to you raping the shit out of me. Whether or not I end up liking it is optional. I apologize that this prompt isn't too fleshed out, but all I really want to focus on is the aspect of betrayal.