Basically Garam knows Jaehyuk is starting to catch feelings but is also deep in denial, so he put an end to their fuckbuddies thing to avoid getting too involved in that mess (just like his friend who only goes for str8 guys and always gets hurt) and little Jaehyuk, who got his ego bruised, got even more determined to annoy the crap out of Garam so in the lastest chap Garam was fed up and told him he will make out with him one last time if Jaehyuk leaves him alone after.
Mmh now that you say that I could see that happening too, but i think that whatever happens he's definitely gonna act like a petty brat again. But also everytime he was frustrated by Garam he always "resolved it" with sex (the time Garam didn't wanna talk about the type of relationship he had with his friend and the time where he tied Garam up after being too pent up from not doing it) and he doesn't seem to have evolve enough from those times to react differently.
I'm trying to think of when he tried to resolve it thru sex after that. He didn't do it for the laptop incident, Garam proposed the blowjob for the sweater incident, it was Garam who came around after they first broke up, and Jaehyuk tried to have sex with other girls the second time to make Garam jealous but he's also still waiting for Garam to come around and be the one to ask for sex instead of forcing him on it like those earlier chapters.
I think his problem rn is his ego thinking Garam will give into him eventually without him changing anything about himself instead of being someone who tries to resolve their problem thru sex.
But he could always disappoint me again lol
His ego + the fact that he seems to refuse the idea that he could have some sort of feelings for Garam. Coz Garam already expressed clearly his anger towards him still trying so hard to get into his pants while maintaining to not have any emotional attachment to him, yet his thoughts are all still about pissing Garam off and not about Garam's reasons for ending the "contract" ┗( T﹏T )┛
But I understand wanting to be positive (●'◡'●)ノ

i wont spoil anything but the last chapters were really sad