I dont understand jaerim at all.

Honestly I don't understand both of them, Jaerim is immature and it's like there's a screw loose in his head. And mc too, even if you are hurt or feel wronged because of jaerim, that doesn't justify his act at all, like blaming jaerim because he is the cause behind all his bad memories with his actor ex, even tho jaerim didnt even know who he was before.