Responses
Indeed, and these memories of guilt and scars will vanish and close up when Heejae truly figures out what he truly wants- when he realises he truly loves Garam- someone other than music. The guilt will go away when he knows for himself that he is incapable of hurting Garam anymore. Garam wasnt a replacement; he changed not only Heejae, but Kruger, Compton- all those broken by music- he made them fall in love with music again.
I don't think the professor had any kind of romantic feelings for his ex manager. It's just the guilt that he sometimes projects on Garam. The guilt that he could have been nice to him and not being a sithole to people who care about him. I would say Garam brings a positive change in his life, and hopefully, their relationship gonna be depends like the fish pond.