Bubblegum Riot

Girl my eyes nearly popped out my head at a double take on your Inhun play-by. THE RESEMBLANCE IS TOO REAL. The others could work.

Lee Dong Wook and Inhun could honestly be twins. It's absolutely insane.

I've tried browsing through other actors for Seungho and Na-Kyum but the features are either to hard or too soft, so my best bets are Ji Chang Wook and Cha Eun Woo haha ╮(￣▽￣)╭

Omg the 'learned sir' picture is on pointtt they look alike and rhat dude definitely looks like he could act out that character fine.

Omg I love it! The guy you proposed for the teacher is spot on, and Nakyum is also very cute, but even though the third guy is also very handsome, he just doesn't give off the right kind of vibe for Seungho... I don't have other ideas though

As far as I've browsed through popular Korean actors, not a lot has stood out to me as a fit for Seungho. He as a character is in a league of his own, so looks-wise, he is a bit hard to find a perfect fit for as opposed to Inhun who is a spitting image of Lee Dong Wook. I've seen a few photos of Ji Chang Wook smiling wide that reminds me of a certain look Seungho does when he's bordering on very pleased and kind of...crazy. Will try to dig around for other possible actors for Seungho though (￣∇￣")

How about Lee Soo Hyuk as SeungHo?

I took a step back from my choice of Ji Chang Wook and browsed through pics of Lee Soo Hyuk, and I have to say that from the eyes up (sort of) and the neck down, yes it could work. But there's something about his features that doesn't scream Seungho like Lee Dong Wook screams Inhun. The resemblance is off for this one (in my opinion, just my opinion). Maybe it's because his features are quite severe in comparison to Seungho, and I've put Seungho's picture side by side with LSH's, and I wasn't really sold. Although Lee Soo Hyuk's stoic expressions are indeed Seungho-esque, but I couldn't see a resemblance. But don't get me wrong, I appreciate your introduction of a new name to the list (=・ω・=)

Lee Soo Hyuk would work as another option for the character of Dohwi from the manhwa Ghost Child, right next to Kim Woo Bin.

I thought of Park Seo Joon for Seungho xD

Gonna rewatch it and tell you ٩(๑❛ᴗ❛๑)۶

Well... since Seungho is so focused on pleasuring Nakyum, infortunately I think that's just the Uke repeating the words destined to In Hun, to Seungho...
┑(￣Д ￣)┍

I suppose so But wouldn’t it be...great...if Seungho had said it, right? If he did, then wow, what a flip from his usual demeanor and attitude towards a person he slept with ヾ(☆▽☆)

Yeah, that would be nice to see him say that, but it'd be a too great thing for him to do at this point, like you say; him flipping from his usual demeanor.
When he first started to respond to NK's kiss (destined to In Hun), the Lord was only aiming to give satisfaction to his attraction, lust for Nakyum and sleep with him. While they were doing it, he finally become more gentle and is acting like a lover (in order to fullfil NK's delusions)...
He's focused on pleasuring him, but is also on the listener side; passive side and just listens to NK. We can see mixed feelings occuring in his mind...

You're just bat-shit cray-cray, lmao. But can't blame you. Who isn't right now?

Those words aren't Seungho's. If you notice the bubbles pattern, when Seungho is speaking, it's round, neatly drawn, in reference to his deep (maybe? I like my seme with deep voice, lol) and steady voice. Nakyum's bubbles are all clumsy, emphasizing that he's overwhelmed and trembling.

As for Seungho's demeanor, for now he doesn't need to speak for readers to know that something is off. The beginning of this chapter was clearly like him, taunting, smirking, and so on. But as soon he wanted an intimacy with Nakyum, something was definitely off. If you see his previous sex scenes, you will notice that this one has more skinship than the others.