SPOILER AHEAD::::: I think there's some cut out parts in the manhwa to make it into full detail when we see Chayun's POV about the break up part. But in the novel, I also thought too that when he woke up that's when Seo Jung broke up with him. It's more like when Chayun woke up(with disssociative amnesia), Seo Jung told him that they're in a relationship. Please, note that his memories went back to days he has yet to accept that he can be in a relationship with another guy. Their family is a Christian(correct me if I'm wrong but more like religious). It's back to the days he thought of him as just sunbae and he was in denial that time. Then boom someone dropped the bomb to him.. Well they had some time away like weeks or a month. During those days though, Chayun really did consider his relationship Seojung. He came to a point that he will accept it little by little.. only for Seojung to suddenly say that he will break up with him. Imagine, Chayun took his time to think about it(he has the brain of 22y/o here and wasn't mature enough to handle everything in his brain cells) only for the same person to say break up. Like all those times he wasted just needed to be discarded. Added to that Chayun has feelings for Seojung that unfortunately he has yet to know it up to this point. The thing though is while they're apart with him busy considering his relationship, his parents had to interfere with Seojung be blamed for everything. That's why Seojung came with that conclusion. Even the part with him never becoming a pilot again.
Omg that make more sense now , so chayun acting like a-hole to seoJung bcs is lowkey cus he's sulky that seoJung dump him (bcs he do hv feelings for SeoJung , slowly developing) yet Seo Jung isnt in the wrong either , cus he's got lots on his plates that time , dealing with his bf accident , then amnesiac , then the parents being homophobes and blaming him , thats why they broke up . Now that i think of it , their story is kinda tragic when put that way :(

So cha yun always say that Seo Jung broke yp with him immediately as soon as he woke up from the coma . But ( from ive been told and novel spoilers ) i thought seo Jung give it some times and actually tried to deal with cha yun tho , then breaking up after he tried . Not just giving up immediately .. can anyone tell me which one is right ?
(Sorry , I dont want to read the novel and spoil myself too much :') )