basically i think what seung is trying to say is that he feels weirded out that he's dating the ex of someone (yuseong hyung) that he used to love so much- and when Section chief leader said "it was a light relationship, it doesn't even matter," he was trying to reassure seung, but seung got even more hurt because that means the hyung he had a crush on for so long was in "a light relationship" with some other person.. i think his feelings are too complicated to sum up in one comment but he's just feeling a mix of emotions and uncomfortableness right now and he wants to express that to section chief leader. he doesn't want to break up though- but section chief leader's mad and not hearing him out ;_;
Can somebody explain it to me? I can't understand it