Responses
I think you may have their names wrong, Dahm is gray haired and Sunwoo is the dark haired guy. Wasn’t it Dahm who called it off so suddenly and didn’t communicate his concerns for Sunwoo’s education and life?
I wish the author would continue the story after Dahm and Sunwoo reencounter each other. I think they deserve a happy ending too :’(

Posted in response to a comment on here but i just need to vent this opinion:
I honestly wish Sunwoo and Dahm don't have a second chance given how the author's ended the side story of this couple. While Dahm had good intentions his actions were entirely selfish. It's been established that his character regularly avoids conflict. That he'd rather bite his tongue or walk away then rock the boat. If Dahm truly loved Sunwoo and had the same level of respect and loyalty to Sunwoo that Sunwoo had displayed towards Dahm, Dahm should have communicated his concerns about their relationship. How hard is giving their relationship space? Or communicating he wants the best for Sunwoo not at the expense of their relationship. The whole point is Sunwoo showed Dahm there's a possibility to pick personal happiness and not be swayed by other's approval. As well as fighting for what's important, i.e. Dahm choosing his own path not shepherded by Dahm’s parents. Isn't Sunwoo part of Dahm’s happiness that he's chosen for himself? Isn't Sunwoo worth fighting for? I completely understand Dahm’s behavior was totally in character, but I personally would be embittered if I was Sunwoo. More so because Dahm abruptly ends their relationship without a single word of explanation. I don't feel sorry for Dahm in the least bit, because he showed he wasn't willing to change his mentality for even for someone he loved so deeply. I don't know I'm not cruel enough to wish Dahm never find happiness but I truly think he doesn't deserve Sunwoo.