Sure, sure. But everything realistic doesn't make for a good story. Or rather, it's about how it's all executed.
Even those "incorrigible" people from your workplace has led a life that made them that way. And such, even a character such as Hyesung hypothetically has a story to tell. We don't have to wind up feeling sorry for him, or that we understand his standpoint, but if we could emphasise with him even just a little, he would become yet more realistic, and a better character.
That’s your option obviously. I think this is a good story - it’s well constructed. The characters are multidimensional, and the way author breaks the chapters is fun. Keeps people coming back for more. I honestly don’t care enough about suh to want to know more about him other ham what the author wants me to know. He was / is an asshole because he thinks people are there for his pleasure. Simple as that.
I think it's well constructed because its premise to begin with is very easy-going. There really isn't a goal except for them to eventually get together, with some hindrances that pretty much becomes the plot itself.
Don't get me wrong, though. I think it's entertaining enough to keep reading, but it's far from a masterpiece.
And what I'm getting at is that us not caring much about his character, and only seeing him as a hindrance is all because he is a badly written character to begin with.
He can still be "saved" as such with something like what I suggested originally, but honestly, not by a lot.
Looking at this, it seems Hyesung's only real purpose is to be annoying. I hope they change their mind about him and decide to soften him up a little, or at least let us see things from his perspective more. As it stands now he is really just a badly written character, and is draggin the whole story down.