@Faiz KZ No, that's because the brown hair girl is his fuc**** ex. Who, especially someone as mentally unstable as the black hair, would want their partner to keep in much contact with their ex? The black hair wanted to trust the blue hair but guess what? He lied, he could've been honest at least. The black hair followed Hyunwoo cuz he wanted to ease his anxiety, his uneasiness about Seojin and Hyunwoo's relationship.