SPOILER
To me it seemed like it wasn't his panic that SH found strange but that he kissed NK even though he was unconscious and that he did it so tenderly and affectionately. The only time he'd ever kiss anyone previously was in the act of sex. Not outside of the act (especially after).
It's no wonder he is confused. He's in love but he doesn't recognize the feeling for what it is.
hsjebshsje SH found out that Inhun called NK a whore/prostitute or something?
Most likely. This wasn't specifically mentioned (the exact words weren't used), but it seems that whomever overheard InHun and Nakyum in the library, most likely heard what was beung said.
Spoilers
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Nakyum fell asleep after they had sex, and Seungho panicked and started checking his temperature. When he realized he was ok, SH kissed NK. By the facial expressions SH makes throughout this chapter, it's clear he feels something for NK and is confused by his own emotions/actions.
Jiwha has a nightmare about killing NK, and SH staring at him in anger while holding NK's body. After he wakes up, he yells at a servant and tries to drink out of a bottle that's already empty. One thing has become clear, Jiwha is NOT cut out for being cold-blooded and has never killed anyone. Despite his hatred for NK I think he feels a massive amount of guilt over this already, to the point of drowning it out with alcohol. If he were to succeed in killing NK he'd probably have a breakdown.
SH didn't buy any of NK's bullshit and found out what happened for himself. Thinking that sending Inhun away wasn't enough, SH seems to me like he's considering other ways to get rid of him now. And at the very end, he recalls his own panic over NK's wellbeing and thinks it was strange.
Overall, I really liked this chapter. We got a bunch of information on the situation and it looks like things are gonna start picking up pace. We can probably expect to see the assassin go after NK soon.