I can't exactly pinpoint why, but these relationships feel horribly plastic. It might be the two-faced nature of almost every character. Or that it focuses too much on the love triangle hooha (which feels weak) and doesn't spend enough time actually fleshing out the characters and what's going on in the rest of their lives and stuff. Or it might stem from the glossy, trying-too-hard-to-be-pretty pasteliche. And the smiling sucks. I realize that makes me sound like a jaded piece of shit, but let me explain. Half of the smiles are fake and the other half feel overly bubbly (which makes them feel somewhat fake themselves). In addition to that, the artist seems incapable of drawing the non-fake smiles in such a way that their genuineness is properly conveyed--such that they exude happiness to the readers. In fact, the artist might just be subpar at conveying emotions of any sort. I don't like the flustered face, the shocked face, the crying face, or many of the other emotive faces. And while I'm complaining about the art, I don't like how a lot of the eyes are cross-eyed and how many of the characters look similar.
The general vibe I get is that of two doms competing over a sub--to spend time with fem. I dislike some of the dumb ways the characters act--like not seeming to care about what Myeonghan (the anxious, sub-like character) wants to do and just plowing forward. Myeonghan honestly feels pretty empty as a character. They include some scheming and rumor-spreading and stuff. There's the idea of gay relationships being judged negatively by the randos in the class, and some characters wanting to keep relationships a secret in order to avoid such judgment. The idea of the sense of isolation that can accompany people whispering behind your back.