Just some mental notes
Garam couldn't help but like Heejae because he found a human in HJ when hj was at his lowest point......couldn't even hold a water glass properly b'cuz of his fever and his leg is limping Somehow HJ can deliver his Chopin with the strength he borrowed from Garam's music and that's when garam heard hj's chopin for the 1st time
Around the same time, Hj discovered the late manager's note and started seeing the white ghost All this time (10 years), he believed manager hated him but it was the opposite When he found it out, he realized he was the one who drove the manager away and started thinking of himself as a knife Before this, he was just a tool for Gem After the note, his mentality rationalize him into a knife that will end up cutting whoever's next to him
Rereading the prev chaps.... I think the interpretation of Garam's concerto by Heejae might be a spoiler for the last season