Heejae was born for music to such an extent that he no longer sees people as human beings. Other musicians are just background music to him, while his students are Gems that he has to polish until they shine, even if that means subjecting them to physical and verbal abuse. The cruelty in him is so deeply internalized that he doesn’t even recognize his actions as cruel; he sees them as necessary evils, something he has to do to polish his Gems and make them shine. He doesn’t care about his students’ mental or physical well-being, and that has had horrible consequences for them, even creating a chain of abuse that eventually affected Compton.
However, after falling in love with Garam, Heejae finally experiences what it means to genuinely care for and love another person. He is so deeply in love with Garam that, for the first time, he actually sees another person as a human being. Garam becomes his anchor to his own humanity. Because of him, Heejae is finally able to recognize the things that hurt Garam for what they truly are: abuse. Things that he probably would have excused in the past as being "for the sake of music" are suddenly impossible for him to dismiss when he sees them happening to Garam.
And that’s what makes it so heartbreaking that he only now notices the scar he gave Garam. Heejae still doesn’t understand that he abused Garam; he remains completely oblivious to his own actions. What he does recognize is the mistreatment Compton inflicts on Garam, which is painfully similar to the abuse he himself subjected Garam to. The difference is that Heejae can see it when it comes from someone else, but not when it comes from him. It is deeply hypocritical, but I don’t think he is being hypocritical deliberately. He is genuinely unaware of the contradiction because, in his mind, what he did to Garam was never abuse to begin with, it was him helping his student to find "his sound". His obliviousness is going to hurt Garam in the future, though, because this boy desperately needs reassurance. And Garam loves him too much, which makes the whole situation even sadder.
Heejae was born for music to such an extent that he no longer sees people as human beings. Other musicians are just background music to him, while his students are Gems that he has to polish until they shine, even if that means subjecting them to physical and verbal abuse. The cruelty in him is so deeply internalized that he doesn’t even recognize his actions as cruel; he sees them as necessary evils, something he has to do to polish his Gems and make them shine. He doesn’t care about his students’ mental or physical well-being, and that has had horrible consequences for them, even creating a chain of abuse that eventually affected Compton.
However, after falling in love with Garam, Heejae finally experiences what it means to genuinely care for and love another person. He is so deeply in love with Garam that, for the first time, he actually sees another person as a human being. Garam becomes his anchor to his own humanity. Because of him, Heejae is finally able to recognize the things that hurt Garam for what they truly are: abuse. Things that he probably would have excused in the past as being "for the sake of music" are suddenly impossible for him to dismiss when he sees them happening to Garam.
And that’s what makes it so heartbreaking that he only now notices the scar he gave Garam. Heejae still doesn’t understand that he abused Garam; he remains completely oblivious to his own actions. What he does recognize is the mistreatment Compton inflicts on Garam, which is painfully similar to the abuse he himself subjected Garam to. The difference is that Heejae can see it when it comes from someone else, but not when it comes from him. It is deeply hypocritical, but I don’t think he is being hypocritical deliberately. He is genuinely unaware of the contradiction because, in his mind, what he did to Garam was never abuse to begin with, it was him helping his student to find "his sound". His obliviousness is going to hurt Garam in the future, though, because this boy desperately needs reassurance. And Garam loves him too much, which makes the whole situation even sadder.
Ack to long