Honestly, the only character I like so far is Jisoo. I'm always a sucker for misunderstood loners who look badass on the outside but are actually sweet on the inside.
MC is kind of a douche. If a friend (even if it's someone like Hwayeon) tells you that someone beat them up on the first day of school to the point where they got a nosebleed, you don't go, "Yeah, but she seems nice and we don't know her side of the story" to their face. And Hwayeon is just...annoying. Clingy, jealous, manipulative people are not my cup of tea, even in fictional works.
We're still pretty early in the story, so I'll keep reading, if only because Jisoo and her bike are really cool.