He definitely had that complex. And it'll be mentioned by other character, that garam only sees the good parts of someone, to a fault. And tbh garam isn't that nice of a person -- he KNOWS how ruined walter's life was because of heejae. He's dating heejae eventhough he knows that heejae had abused someone to the point where they can't even listen to rachmaninoff because it reminds them of heejae. Like....that's really something.
Yeah they’re both so toxic that they belong to each other so much hence why they are my otp (sorry Walter, you are loved but not deranged enough for this main couple. Also Walter, you’re a total bottom to me even if you dream of topping Garam sorry not sorry). I can’t help but think Garam’s need to feel special by being the only person to Heejae starts as a coping mechanism for the abuse he endures and the need for validation that he can find a life in piano along with the guilt of Heejae risking his hands to protect Garam. Then eventually it evolved to full blown obsession driven by his jealousy of Clarens and the isolation Garam faces in New York which is not only far away from his home country, but distant culturally and linguistically with Garam being dependent on Heejae and the people Heejae has hired. The only person Garam is friends in NY outside of Heejae’s sphere of influence is Walter, but even Walter only approached Garam due to him being Heejae’s student. Hell even Garam’s current manager is under Heejae’s control. Garam craves to feel needed and special so desperately that he will embrace Heejae’s faults by saying no one else can endure or understand in turn making Heejae emotionally dependent on him as much as Garam is both emotionally and financially. Garam would probably not want Heejae to apologize to his former students for abusing them because he wants all of Heejae’s love and care to himself even when Garam can empathize and see just how broken Walter was at Heejae’s hands. This can be seen by how apologetic Garam is bringing up Heejae to Walter, but never once really confronting Heejae on whether or not he actually regrets his past teaching methods instead choosing to ignore it so they can continue on being a happy couple. Garam has always chosen a relationship with Heejae over anything else even for his own good when Garam tried to leave Heejae for a better teacher, thwarted as soon as Heejae started kissing him.
Garam on the surface is a people pleaser, seemingly passive and polite, but is just as possessive as Heejae and as selfish demanding Heejae’s everything even if it is Heejae’s more cruel tendencies. Which is why I don’t think Garam is a naturally born masochist but only enjoys the pain Heejae inflicts because Garam knows when Heejae hurts Garam hes not holding back. After all Garam takes great pride, almost fanatically deriving his worth and identity from, by understanding the professor, enabling violence as a sort of way to validate his feelings that he is the only one that could understand Heejae. I can’t wait till we will see him transform his sound and soul for the concerto just as he has gotten colder after being closer to Heejae than anyone ever has. Ah they’re so toxic and need therapy (both individually and couples therapy) and probably medication but they are my mentally ill toxic ass couple.

ppl make out garam to be sm super innocent perfect victim who's too good for heejae but i feel like this ch kind of showed how garam can be kind of pretentious n selfish in his own way? i think he has this saviour complex, tht's esp highlighted w heejae, considering how broken of a man he is. garam's egotistical in the sense tht HE'S the only one who can withstand n love heejae. n this might be a fetch but him ruminating over how compton was smone who (allegedly) overcame hj might be making him feel jealous..? indicating his own possessiveness/ obsession over heejae.
so tht makes me wonder, if my guess is right then 'garam gets upset when he finds out abt manager' might not be the straightforward progression we expect cus the complicated feelings of finding out there was another person who culd endure heejae (not love, endure specifically) wuld i don even kno. JUST i don think it'll be as simple as him just getting upset. like i think thr betrayal isn 'heejae sees manager in garam' but rather 'manager was smone who culd endure heejae' cus THT is wat challanges garam's belief/ ego. but liek ion kno, just my theory huhu ♀♀