Well I’m not really sure about this but basing from the raws, which i obviously didn’t understand cause i dont speak korean...
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Beomi and the director were once friends and were attending the same school together with the blonde girl but i think the director sold beomi out to his father. I think the director kept tabs on beomi and reported it to beomi’s father that’s why their relationship fell out. It might be because the director was jealous of beomi? I mean back when they were still students beomi was able to act well effortlessly. Im not sure tho

I think beomi was protecting his director friend, hence he had to cut him off rudely like that.
I think he had to protect him because back then he had all those weird scandals hence he didnt want his talented friend to be ruined by being associated with him.