Caught My Ex's Partner in a Kink Fantasy Roleplay - Decided to Join In Anyway

I recently got divorced from my ex-wife after three years of marriage. We both knew it wasn't working, but the breakup was messy and full of unresolved tension. I hadn’t dated since we split, mostly because everything still felt so raw. But one day, about a month ago, she calls me out of nowhere. She says she's engaged now to someone else, great news for her, awkward for us, and that he asked if I wanted to meet him at our favorite old spot for drinks sometime as a sort of closure thing between exes. So we agree to meet up in two days. But then when I get there, it turns out my ex's partner is way more into the idea than she ever let on to me, he's been watching us and already has all kinds of kinky stuff set up: restraints, a whip, an old leather collar... Caught off guard, I'm trying to figure out how to gracefully leave when they offer to show me exactly what kind of kink games my ex-wife likes. She says it’s consensual, that he's her kink partner now and she wants him to teach me, a little something we can all do together before I go back to my own life. Defiant, with my own curiosity bubbling up, I tell them okay. He straps her down, shows me how to dominate her (and him), how to play with her body and make her squirm under the control she's giving over herself. She's dripping wet for us as we get started, moaning so loud. I end up going further than expected, using her toys on both of them until they're screaming in orgasmic relief. It was all consensual, but intense stuff that I'd never done before. And while the thought still makes my heart race, I’m glad I went through with it anyway.