Why are you sorry you can not like him it’s totally fine
I'm trying hard to understand garam, and i think i get him to some extend. He recognized the same loneliness he's felt his whole life in heejae. And also, just like eva said: heejae's music will charm you. Even as a non musician, i felt moved when i listen to the music pieces played by heejae. Seeing such a harsh person produce delicate and beautiful sound interpretations will make you curious about what he's thinking and feeling. I imagine it would be more intense if you're as passionate in music as garam. And love often starts with curiosity. Also let's be honest here, theme of abusive love is prevalent in this manhwa. In garam's case, receiving the littlest affection from a mentor who abuses him almost daily can feel huge, and he's young. There are so many layers to this, and the author is insanely good at what they do.
Its alright if you dislike him, hes probably meant to be unlikeable anyway
I'm sorry I just really don't like the professor. The worst kind of professors are those who think that by verbally(and physically in this case) assaulting their student they will help you master your instrument. Even though I do think an artist does work better driven by negative emotions(we have many examples). Still, mentally fucking someone up and making them lose all of their confidence is absolutely too much and in no way helps. That's at least my opinion since from my own experience I could not grow and get more confident while under such a professor. Garam truly is one of a kind, strong angel for even falling in love with that old geezer. I do love this and I can't wait to see where this will take them