The author always leaves holes in the story to solve later so, kind of a spoil and a long explanation, but
Chuljin met Minwoo, Suyong and Jaehyun in highschool, somehow he messed up with them (not sure how he messed up with Jaehyun, but he’s the reason Minwoo hates Jae) so now only Suyong still thinks good of him (in a way, since they fought about Jae being in a relationship with Suyong).
At the beginning of the series, Sungtaek tells Norman that he downloaded an app out of curiosity (kind of like Grinder) and this J person he matched with and got close to, told him stuff about Minwoo making up stuff about Jaehyun being a thief. Minwoo looks it and it turns out to be Chuljin. Later, when Norman is living with him he says that he was his first love, cries and gets drunk.
Also someone else from the Weightligting Department says smth about J being Chuljin, and Minwoo sleeping around, I think it’s the dude that Norman threw his drink to.
So, Chuljin is an actor and a celebrity, that’s why he is not in college, and his personality is kinda fucked up because he tries to meddle in everyone’s business, kind of like a superiority complex, idk.
At the end, he likes Minwoo and is trying to get him back, doesn’t like Jaehyun, he also appreciates Suyong and that’s why he tells him not to get close with Jae, he has business with Sungtaek because he met him online, and later he gets kind of close to Norman only to his own interests.
Oh, he also met Norman in hs but they were not close, more like a friend of a friend situation
Can someone please remind me who Chuljin was and like what did he do?? I don't even remember him talking with Sungtaek lmao why were they even talking and why do they all know each other