[M4M] You want to steal her from me
You are friends with my wife. Maybe you met her through running club, or through guitar classes, or maybe even both. You have really impressed her with your talent and physical fitness, and you spend a lot of time with her doing these hobbies since I am not interested in joining her, and also feel insecure about the things you are good at.
Through these activities, you've grown fond of her, and you can tell she's attracted to you. You know she's married to me, given that I've met you while picking her up from your fun outings. You don't really have a strong opinion of me, but you can sense that I'm passive and submissive, that if you really wanted to, you could probably start an affair with my wife. But being the gentleman you are, you want to feel it out first with both of us.
Kindly - but firmly and decisively - you make your move. You're a confident, handsome, charming guy who has already made a positive impact in my wife's life. You consider her a good friend and want to take things to the next level. You know she's interested. ;)
Elements of emotional cuckolding, emasculation, and D/S dynamic desired