I'm not really sure but the whole sequence is basically they both moaning so I took it as this. He's turned on.
I think that even if they started the sex under other pretenses, they both got into it and Nakyum is letting himself moan and enjoy and all the ! is for this purpose. I think we only will know for sure when we get the official translation. :)
OMG. I have to say the chapter is jam packed! It's such a development from Nakyum to ask and beg for it. For someone who is sexually repressed to ask for it? Damn what a feat! I feel like I should thank Inhun for it. Lol. Yet the poor boy had to experience such a convoluted situation. There are so many layers in the situation that his poor heart couldn't take it, thus crying like there's no tomorrow.
Then there's another wall from the many walls Seungho has broken down by Nakyum. The author is truly killing it.
Chaper 42 raw was sad but also kicked up a notch the intimacy between NK and Seungho. Opinions below are my own (mild spoilers).
What I love about this chapter is that Seungho ends up having sex with NK even knowing that he is being used for comfort. We know from the beginning of the story and also because of the time he got drunk that NK usually uses alcohol as escape for his sorrows. This time however he is using sex to forget and who's best to pound him into oblivion that Seungho? He wants comfort through sex and he gets it by being honest and frank when Seungho asks him if he is doing this under Inhun's orders.
Seungho may be a horny dog but he was not up for it when he thought that NK was seducing him because Inhun told him to do all that. He however can't help but cave in when Nakyum gives him both a subtle confession that he desires Seungho and then calls him off on the cruelty of refusing him now that he is asking when he had no problem taking it before when he rejected him.
Nakyum saying something like: 'when I look at you, my Lord, I'm scared but my heart beats faster ... even when I hated you all the time you embraced me without hesitation ... so why don't you embrace me now?
So much packed in this exchange. First, Nakyum's conflicting feelings about Seungho is the backbone of this story. He fears and then hates Seungho but he is also attracted by him. People seeing NK gradually letting himself enjoy the sex with Seungho, a man who scares and even raped him, quickly just calls it a Stockholm Syndrome but to me this is more about things that were seeded way before the sex. There are countless scenes showing NK was being seduced by Seungho lust and was drawn to him. Nakyum literally dreamt of an aggressive Seungho dirty talking to him .... it is not uncommon to feel attraction for what is dangerous, powerful, dominant and for someone so innocent and sexually repressed as Nakyum, lust may be more powerful than hate, even more when Seungho does things that show cherish and care (like all the things with the doctor, medicine, his room, etc). I think, by the way, that Seungho is already in love with Nakyum so even unwillingly gestures of care escapes him and Nakyum is also feeling that, especially in the moments Seungho surprises him with softness when he expects the worse.
At the same time that Nakym answered like that, he is also shaming Seungho, what is a thing of beauty. Seungho has no answer on why he can deny sex now that he is being begged to while he freely took it before without consent. He knows very well he is being the alcohol now for Nakyum and this is a bit of blow on his pride but he caves in and gives Nakyum what he wants.
Finally, this is the first time Nakyum is directing Seungho during sex and I think that even if Seungho is still flustered because of the reason behind the sex, watching Nakyum being vocal during sex and needing him must be even more of a plunge for Seungho. I wonder when he will admit he fell in love with the lowborn peasant.