facts
Joowon doesn’t love Haesoo. He has an unhealthy obsession with him and thinks because they were in each other’s lives at some point that Haesoo owes him his attention and affection. He’s always thought he could come and go in his life, no matter who Haesoo was involved with, snap his fingers and Haesoo would be in his bed, until he realized he couldn’t do that anymore and that shocked him to his core when Haesoo said no more.
I disagree. Imo it's rather clear Joowon loves Haesoo but their past and situation and him being afraid of rejection impacted his actions and he started making mistakes. And didn't progress their relationship (same as Haesoo).
He also tried to protect Haesoo in his own way.
Future chapters imo confirms even more that he loves him truly.
And he thought both of them had feelings for each other. That if for him Haesoo is number one, it's the same case for Haesoo.
He will most likely end up with Joowon which I totally support. Honestly, Joowon has always loved Haesoo but it was hard because they are ex-stepbrothers. Joowon wants to love Haesoo but can't because he also knows Haesoo always wanted the affections of his mother (which his mom fails to show). So to give Haesoo what he really wants and needs...he tells him he doesn't love him but that was never completely true. Joowon sleeps with Haesoo throughout the story because he, too can't resist not being in a world without Haesoo and he knows it, too that he won't be able to love anyone else. Taku on the other hand has always been known to use people because he's a workaholic. He'll do anything to be satisfied. Despite, the fact that he claims and shows that he "loves" Haesoo...we all know that if he were to choose between his job and reputation against Haesoo...he would rather choose his job.