Side note, the reason why I said it's a gross overreaction, recently I read Rivalry, where it dealt with similar scenario of emotionally stunted character doing something bad before they are officially together. In that case, it was having encounters with other women. In other words, cheating. It was big enough that they were considering breaking up, but luckily they reconciled fairly fast after having a good talk.
What Dohu has done in contrast pales in comparison. Yet, the punishment he got was infinitely more harrowing. It's understandable why Juheon's reaction is so extreme considering his traumatic experience, which the main character of Rivalry didn't have. What I'm trying to say here is, in an emotionally healthy relationship, their break up is unlikely to happen. This break up only happened because we are dealing not just one, but two traumatic people. There are those who only blamed Dohu for their fallout, when in reality, both sides have problems that need to be addressed if they want a long and healthy relationship.
To give people an idea of what kind of psychological damage Juheon has inflicted on Dohu when he left him without any explanation, silent treatment is considered a form of abuse. Juheon has the right to be angry or breaking up with Dohu if he feels this relationship does not work, even if in my opinion, a gross overreaction to what Dohu has done, Juheon still has the right to do so. However, Dohu is entitled to have full closure to this break up and not a full on ghosting without even saying why. This is why Dohu is left completely broken as he has to live without understanding what had happened. As he said it himself, his time has frozen still during those 4 years.
If they get back together, I hope the story would address this, because I don't think Juheon himself knows the kind of damage he has done to Dohu because he foolishly believed Dohu didn't care for him. This is the kind of thing that will leave a lasting trauma even if they get back together. Dohu will forever be afraid if Juheon could just be up and leave him.