I think the fact that Subin kinda acts slightly indifferent with Hyeonwoo shows how much he's grown.
I like how much he changed it's good they are not 19 year olds or something, even if I say it Jun is perfect person who is actually better to spend rest of your life a person who you can look up to, mature not hyunwo who is still crumbling in past with meanie behaviour that he would show he hasn't grow up at all only thing that has grown in him is fame , may be subin character developed more cuz of staying with jun which is good.
this is still one of the best bl stories i've ever read tbh. the raw emotion? and the fact that subin matured so much, like I remember the first few chapters when this was just posted here and the people in the comment section was just so pissed at him. like man, i'm just so, so proud of him.