
All the thought bubbles are NK's. The reason the last images focus on SH's face and not NK's is because those thoughts are in complete contrast to SH's own. He wants NK to tell him what's on his mind. He wants to know why NK is so submissive. He wants there to be more between them than just sex. That was a face of desperation right there.

SPOILER
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My heart hurts for both of them. You can see the pain in SH's eyes as he realizes NK is acting like a prostitute who'd do anything to please him and not a lover who cares for his partner. SH obviously must have believed the change and NK's meekness was because NK had started to grow fond of him but now he knows that it's not the case and it's a painful reveal.
The only reason he snapped and started acting like his crazy self is because NK refuses to answer him and continues to act like a prostitute. SH wants the old NK back. He wants a person, a lover, not a subservient prostitute.
When he repeated the phrase 'I keep you around for this' multiple times you can see that he's realizing that he doesn't in fact keep him around for that at all. That he cares for Na-Kyum and that it isn't all about sex.
I truly cannot wait for the next chapter. I want NK to tell him what that fucker In-hun said and I want SH to clear up this misunderstanding and then go stab that four eyes and send him to hell.

I'd punch that ugly jealous bitch servant in the face and then pull Na-Kyum into a massive hug and tell him how precious he is. Then I'd give SH an earful and tell him that he better treat our precious cinnamon roll better or he'll get stabbed in the dick by me and the fandom. Next I'd head out to deal with four eyes, no name and the spurned exes (╯°Д °)╯╧╧
Tbh I really would not mind Nameless getting together with NK and the two of them leaving and finding happiness elsewhere. SH and Ji Hwa honestly don't deserve either of them. But I know that's sadly not what Byeonduck has in mind....