It was mentioned before that Woojin wanted to imitate Wooyeon so he started becoming an honor student, and because of that, his mom's attention shifted more towards Woojin. He got jealous of that so he started acting cold and mean to him because "Woojin is stealing his family" from him.
Ah, I forgot about that. Still doesn’t excuse Woojin for manipulating his mind like that, but that is pretty shitty of Wooyeon.
Actually, I went back and read and something seems off because he remembers hating him from the very beginning, but the mom is saying they got along at first. Someone had their mind played with it seems.
Woojin probably kissed him or something and Wooyeon didn’t know how to deal with it, so he just started acting mean towards him. Still doesn’t excuse Woojin from hypnotizing him all this time. I think that’s why I can never get in the “Woojin is so hot.” train. Playing with someone’s mind is a hard no for me and makes him gross.
I also don’t get everyone wanting a whole side story about the seniors being a couple? They’re not that interesting to me. One is a jerk and Wooyeons “boyfriend” is kind of just spineless. I guess we’ve just gotten used to there always being a side couple.