I used to feel that way too. But I think it has something to do with the other seme. In the dreams, he told the uke that he has the smell of death on him and that people would be able to sense it and be repelled by him. I think that explains why the gray haired guy swings back and forth between being sweet and a jerk. I think he genuinely likes the uke but the curse(?) Is making him act like a jerk. Think of the weird things that were happening and how some things didn't add up. But I'm sure a good looking popular guy like gray hair is probably has some jerk tendencies, but nothing too unbearable.
Yeah, we need more clarification about that.
I dislike the sunbae , aside from the fact that he behaves toward him and uses him without makeing him feel good, he hangs out with losers and lets them bully the MC.