Sangwoo’s attractiveness is a really interesting part of his character.
Villains are commonly presented as disfigured or disabled. This is actually such a prevalent part of media that it’s discussed academically. Micheal Myers, Jason Voorhees, Two-face, Candyman, Leatherface, Darth Vader, every Bond villain, and even the villain Dr. Poison from the ‘progressive’ Wonder Woman is given a facial disfigurement as a symbol for how evil they are. And all the protagonists in these stories are beautiful, and they are beautiful because they are good.
Villains are made disfigured, disabled, ‘unattractive’ as a way to show that they’ve lost their humanity. It’s that ‘evil makes you ugly’ trope or the ‘evil cripple’ trope and it’s rooted in ableism.
KS handles this trope in an interesting way. Bum has a limp, he’s disabled at this point, he’s described as ugly, creepy, and he’s reviled by other characters because of this.
Jieun is threatened merely by the way he looks, even though he’s ultimately harmless. Sangwoo on the other hand, he’s loved by people who know nothing about him because he’s beautiful. He lures people with his looks, the audience is affected by this too, they’re supposed to be and they know they are.
The subversion of the ‘evil makes you ugly’ trope by switching the typical physical attributes of the protagonist and antagonist is one of the more thoughtful parts of this manhwa. A disabled, ‘unattractive’ protagonist being tormented by a beautiful villain is a critical part of the story. We’re shown how differently they’re treated by the outside world.
It’s why these scenes are so painful, Bum is constantly looked down on because of his appearance, while Sanwoo is looked up to, which is reflected by the composition of panels. Sangwoo is always standing above everyone else in the frame, that’s how the world views him, and Bum is always below.