Some people are only nice while they're gaining something from it. Once they stopped feeling special for being nice they also stop being nice, I think that it's the case here
Definitely not. Considering her situation, there was really not you can gained from her, even she herself thought so. He even went out of his way to work for a mouth straight so he could buy a phone for her to text him. I truly believed that he really loved her when they were young. 13 years is a long time, people changes, considering their tough situation for years, he simply couldn’t withstand it and aimed his frustration at her, you could tell he still loves her but it’s no longer as pure, taking advantage of her kindness, taking it out on her, making up excuses for his behaviour and painting her as the problem. He stills love her but he doesn’t deserve her.
Bro was nice asf, how can a person change so much? But well guess na haesoo is lucky in men unlike us