He is in the process of making it official, if he can get through that thick head of hers.
But it seems he is not rushing to not make her uncomfortable, which is nice. He also wants to take care of her. I do think the care should be from both sides though. I don't mean she is a bad person. I just say that since I know from experience that only depending on others is not fulfilling.
But maybe she will mature if they get kids or dogs or whatever. Or if Chanmin gets sick she might have to take care of him and become more responsible. It doesn't seem like the manga will address that though.
She's not think headed.. She literally told him that she's uncomfortable (of sudden dynamic change). They both know they have mutual feelings
So chanmin DOES admit they're a couple huhuuhuhhuuhhuhuhhuu,