I think, it's because he felt "afraid" of doctor's attitude, and the he remembered that he likes the main guy, and want to be close with him, I guess...
he sees the doctor as "competition" and wants to become closer with hyeon without being weird lmao
I asked ‘cuz in the comments I saw some people saying he “did it for his friend” and it got me confused
At the beginning when he asked him why he moved, he bluntly said because of a fight. And the friend said he could see how he liked the fact that he couldn't say anything more. He sees this guy who seems to have the upper hand over him, and friend wants to be closer to him. If that makes since. Hard to explain because can't spell names from top of my head
Wait I got a bit confused, can someone explain to me how the flashback made him suddenly change his mind?