he's manipulative to start. and then he's selfish to end. He never once did anything for someone else, without an ulterior motive to ALSO benefit himself :D and he's the least developed out of the three.
joowon: actually matures, reflects and recognizes all his faults (the faults: taking haesoo for granted, being so arrogant in his decisions to keep their r/s undefined that he missed how haesoo was suffering, not wanting responsibility for any problems their r/s may cause but still being possessive). Anyway, he clearly tried to become someone better. He realized everything he did wrong, drops all his possessiveness, and makes multiple sacrifices for haesoo's sake WITHOUT asking for haesoo to take him back. Instead he shows that he's literally willing to be anything haesoo wants him as, even a brother or friend-- even after haesoo lowkey said he's not worth loving if it means he might lose his mom, and dumps him for another guy :D Joowon literally still tried to protect HS till the end, and even loses his drama as a result.
meanwhile haesoo: fully recognizes by the end how he mistreated joowon and regrets it all very deeply. he stops running and denying his feelings, which may seem minor to you, but it's a HUGE feat for him, considering he was guilt tripped for 7+ years by his mom and made to feel absolutely horrible for loving joowon and that he was a failure of a son for this.
now, there's taku. he literally does not have any moment of self reflection??? he fully recognizes his own shittiness from the start, admitting he tried to guilt trip haesoo, manipulate him for his own interest and exhibition, displays haesoo's hurt emotions out of intrigue, etc... but doesn't bother to really change at all. even in the end he's like "told you im not a good person" and just seems to accept that. i understand ~love~ can make you selfish and somewhat vindictive though, so i sympathize with him to that extent. but it wont change the fact that he's underdeveloped in comparison.
oh yeah here's the post that fully explains what i mean by "he's manipulative to start, and selfish to end". tbh with his manipulative nature, it's not as if joowon and haesoo are better to start anyway. but as the story progresses he remains the most underdeveloped to me sooo:
http://www.mangago.zone/home/mangatopic/9517513/
and i say more here~ (the replies underneath, between me and another user @jungzi explain a bit more of why i think what i think): http://www.mangago.zone/home/mangatopic/10579920/
if you seriously disagree with everything i said, feel free to discuss with me kk
Idgaf about Joowon and Haesoo's complicated love affair just give me Taku's side story already