Technically it's not for the manager but for Heejae, himself. However it's heavily associated for the sole fact the manager is the only non music professional that Heejae allowed to touch the piano and played it in the first place. So it makes sense for me and Heejae that he composed a new piece for Garam since he does want to put it in the past. I don't think it's just anxiety alone. The manager plays a pivotal place in Heejae heart because he carried that sort of understanding, resilience without any bias and actually tried to understand Heejea's heart AND music regardless of the brutal facade he builted. Notices others only tolerate Heejae because of his music. Remember the note the manager left behind for Heejae? Heart breaking

First of all, I’m glad this is censored because I couldn’t have handle seeing Professor’s pianoforte in all his splendor (ofc I can, I’m just pretending).
Second, the professor always taking care of Garam’s health through nagging reminded me who much of a couple they are, they are so fricking gay. I’m always tell my bf to apply skincare and put fucking solar protection . So I related to that.
Ch 186 was truly romantic, Heejae prepared everything for a perfect date, watching Monet, eating at a nice restaurant, going for what I think was jazz and enjoying a good evening to end it up with the song. A song were the professor throughout the whole process had Garam in his mind.
I’m glad, bc many people complained that the professor first OG song was for the manager, which wasn’t, but okay. Second, always saying that he was thinking of the manager which again he wasn’t it was his anxiety in the form of the manager. But here, no manager, no anxiety, just the feeling of being in love and apart from your baby boy.