
I'm glad you loved it. Thank you.
Seungho raped Nakyum and was so rough because he is angry at him. From Seungho's perspective, Nakyum never expressed him any kindness. Even when he expressed his feelings, Nakyum return them by getting out of his grasp. He believes that Nakyum likes only sex between them like a friend with benefits. Like I said, Seungho knows deep down that something is not right. He noticed the bruise. But Seungho being Seungho is now focusing on the sex with Nakyum. Seungho is so obsessed with Nakyum, he doesn't want to hear anything from him.
Like you said Nakyum is really terrorised by all that is happening. His feelings came to light as he realised that he doesn't dislike Seungho. But the act happening at the moment mixed with what happened before is too much for him to handle.

The next chapter could go many ways. It could be a continuation of the sex scene but I hope the author won't go that way. One chapter is clearly enough for readers to get the point.
It could also be the aftermath. If we go by comparison of the first forceful scene, he could be regretful, but not enough to know what he feels. He will use Nakyum more for sex and less for his paintings.
He could also inspect thoroughly the bruise in Nakyum's hand, but I doubt the author will go for that. He needs someone, Servant Kim for instance, to push his buttons and make him realize that something doesn't add up about Nakyum.

You were right ! The new chapter was a continuation of the sex session and sadly Seungho fucked Nakyum outside in front of Kim. Just image how Nakyum was feeling at that time ? He’s very wary of what others think of him .. and he was but naked without clothes and no shoes I really .. my heart break so much for him I really fear the next chapter what will Seungho do to him for the next days ??
Also I am glad we see this woman . She seems to be the Noona who grew with Nakyum . She have manservant so she seems powerful I hope she will help him
That was a gruesome chapter like I predicted.
The panels are most of the time blurred, depicting the harshness in the act. Seungho wanted things to be done like he supposed Nakyum would like it and didn't listen to his pleas to stop. That was nothing more than a role play for him. This chapter his comparable to his early orgies. In those, there was clearly no sign of closeness. He used those sessions to release his stress, to forget and just enjoy the moment of lust. In this one, there is that plus the sense of regret to have choose to blurt out his feelings. Like I said previously, there is nothing to lose for him at the moment.
During the sex scene, he noticed the bruise and stopped for a moment. What is ambiguous about it is that's the same place Dukjae hurted. At the same time we see the rope bruise, we also see the same mark Seungho tried to avoid when saving Nakyum by beating the servant to death. He knows that something is amiss, but is too blinded now to stop.
Nakyum is clearly suffering in the act. He doesn't have the upper hand anymore because Seungho won't listen to him. His begging is falling into deaf ears right now.
I said in the previous chapter that everything happening will unfold as a rape if he doesn't talk and that was the case. But there is a new take which is his feelings. Nakyum realising that he doesn't dislike Seungho was the saddest part for me. He is sorting his feelings during the forceful act. As I'm on the side of those thinking he should have talked, him not talking also has is sense because his mind is tired. There is too much information for him to process. But that also makes him fall in the trope of the damsel in distress type of uke.
Concerning Nakyum begging Seungho to let him go, I will bring another chapter to comparison which is chapter 16. In chapter 16, there is a playfulness in Seungho's handjob. He is teasing Nakyum, making him discover the pleasure of the touch of someone else (or as he believed, relieving Nakyum from all his pent up desires because he thought at that time that Nakyum was no stranger to sex intimacy). He said "I heard you, Nakyum... I'm letting you go there!". The connotation was much different, he had a teasing side.
The recent chapter on the contrary has a mark of possessiveness. "You want me to let you go?... That I cannot allow... I will never let you go." were his words. The noble is claiming the painter as his property, adding a new dimension to his obsessiveness.
I will add that to those claiming it as "romanticising the act of rape", there isn't any type of romance in any of the panels that the author drew for the recent chapter. It was hard to look at (not for me, I'm immune to those as my view of what is reality and what is fiction is dissociated), it was hateful, there is an abuser/victim situation and that was beautifully depicted by the artist. It was really different to what we were accustomed by now, harsher than the blowjob or the forceful sex scene.
I hope that Kim will bring light to this mess of a situation. As for our mains, there will be a new rift between them.