Hating on the MC (as in, the main character, who is female, Hana; I just hate it when people can't realize MC means that) is easy. She is easily dislikable because...of a lot of reasons.
But I ALSO don't like how the author has made Geon Woo here, with his obstinate attitude and refusal to listen. It's made worse when we see the easy alternative. Instead of him refusing to break up when she says it, he could've just proposed this from the beginning. When they were outside their apartments and she asked him to break up? He could've just said this then. There was no real reason to make him be an actual bad person by having him straight refuse to break up. He didn't even try to convince her at the time. He just said no, go home. Then it's multiple days later that he says this.
It's weird.