
Actually, in the intimacy of the room, that's how BSDM works... slaps and so its pretty common in this kind of relationship, that's why MD asked if they were ok with it.
After you state that both partners are ok, you can role play and act in a variety of ways.
For that kind of confusions is that exist safe words, so you know when to stop. MD still hasn't done anything wrong... yet, at least.
Ps: what is your first language? XD I got curious

Look a few posts up at ManiB25. MD is definitely trying to make Chanwoo use the safe word and finally know his limits. Chanwoo has SM all wrong and needs to learn that it's only fun if both parties are enjoying it, it's not just about the Dom doing whatever he wants. MD probably hates having to do this but he's realized this might be the only way Chanwoo will realize and is giving him plenty of chances to say no, but so far Chanwoo won't back down

Sigh. Yeah that's why smirked in mean way in restaurant. Because he wants to help Chanwoo. The main motivation is clearly revange and grudge.
And it's really not the best method to approach the subject even if he really wants to help him. He nearly strangled Chanwoo once. They are subs who don't know their limits and they can't just learn them. Chanwoo is in really fragile state of mind right now what makes it all worse. And think about his abusive bfs.
Ok before this chapter I was at MD side because Chanwoo was too greedy and didn't respect MD feelings and went to ask him for dating someone else. But I didn't expect this at all!!! I didn't like what MD did in is chapter and now I'm mad asf. MD YOU ARE NO LONGER DIFFERENT FROM THE TRASH PPL WHO WAS CHANWOO DATING BEFORE.
U DIDN'T HAVE TO SLAP HIM LIKE THIS AAARRGGHH
And I'm sorry for my bad English ╥﹏╥