Yes it's the first time and it's quite sudden indeed
Not “I like him” perse. But that’s because he doesn’t use that kind of vocabulary because this is the first time he’s experiencing this kind of relationship. But it’s been hinted several times and Mokhwa actually said how he’s gotten used to Nakwon’s warmth and presence and how he’s actually looking forward to it. He always mentions how annoying Nakwon is because he’s too extroverted. But he likes his company and he has mentioned that and it has been hinted that Mokhwa like Nakwon too. It just that due to Mokhwa not been used to relationships other than the ones he had out of obligation with his mafia group, he doesn’t know quite yet how to put it into words.
Also, am I just forgetting or has Mokhwa never really mentioned actually liking Nakwon before this chapter? But then he goes and drops that he's been ready to date him for months . . . It's cute tho. Definitely makes me look at a few things differently now, in a positive(ish) way ๑(◕‿◕)๑