I actually ship nakyum with seungho tbh. I know that S doesn't treat N right but we have to consider S's past as well. It's evident he has suffered a lot that's why his emotions are a disaster but still he loves Nakyum enough to care about him and all, which he doesn't for anybody else.
The disparity between a nobel and a lowborn was really great in those days so of course he's got that attitude (?). He got jealous and upset when N looked at the other guys in a way he never looked at him and all. Even Nakyum cares for Seungho and it's evident.
But if they are happy without each other (i doubt it. I hope N helps S heal from his past and S gets over his pride/attitude/idk what and treats N with all the love and affection he deserves.) then ofc I'll support them with all the pieces of my broken heart ahaha!
I just wanted to place my opinion too since I see a lot of people hate on Seungho without trying to understand him. He's toxic i admit, but it's his past that made him this way. I'm sure he'll recover one day and become truly worthy of Nakyum! x