Terrible Ex-Boyfriend

[He said our first night was disappointing, said he was bored of me, and even cheated— yet now this terrible ex-boyfriend keeps trying to get close to me.] My ex-boyfriend lives next door. Yes—the same ex who cheated on me and treated me terribly. “My girlfriend? We’ve known each other since we were kids, so I’m only dating her out of obligation. Honestly, I’m getting tired of her.” Cheating wasn’t enough—he also talked badly about me behind my back to his friend. There was no reason not to break up. But at some point… his behavior started becoming strange. He kept sticking around, bothering me, clinging to me at every chance. “I’m not just your old next-door oppa. I’m the ex-boyfriend who adored you like crazy.” He even said outrageous things in front of a new guy I had started talking to. What on earth is going on with you, Kwon Doha? We’re broken up. Why are you acting like this now?