So I while back my wife (both in our 20s) asked me about sexual fantasies, I brought up that I've thought a MFM or MFF would be hot and we left it at that. She met a manager from one of the chain stores she works for (she's also a manager) who was always flirting w/ her. Long story short she asked if she could go on a date w/ him, I said no and she brought up the whole mfm saying it'd be similar, but I kept saying no! She would bring it up here and there till I said "ok" but only if I can tag along. What happened after was surreal. After she agreed to go on a date w/ him he showed up at her work and when they were alone he made out with her and groped her. She texted me and said they were going to f*** that night, So as agreed they were cool with me being around so when she closed her shop I got there and he was there, he opened the front for me b.c she was in the restroom getting ready, he had a grin on his face and said "hey." They decided to do it at her shop. She came out wearing high heels and lingerie, I was speechless, partly due to shock knowing that this other dude was seeing her like that. Anyway they started making out and went back to her office, I went back for a bit and saw her on her knees giving him h***. I went outside for a smoke and felt super shaky and anxious. When I went back in, she was on her desk moaning and he was just giving it to her, I couldn't watch so I walked across the street to a Whataburger and had a drink. When I came back I went to the back and they were making out, they had just finished. He kept grabbing her butt and kissing her, what got me really annoyed was that they ignored me, she was all smiles and laughing. We got home, had a small argument and went to bed. We didn't have s** for a couple weeks after that. She flat out told me that she wants to keep sleeping w/ him. I regret saying yes b.c when I ask her to stop she brings up me letting her try it and now they do it regularly at her work or in a hotel room.