I think its cute! Hyeseong needs to move on from the other girl, and the manager is smart, patient with him and understands him. But right now I think they're just misleading us, somehow, we don't know for sure whether they'll end up together.
I don't really find it 'cute' but discomforting and too sudden to be seen as thorough romantic development between two people. I don't mind him moving on from the other girl, but I feel like his chemistry between the other girl and his manager are very similar, in terms of being non-existent and feeling forced just for the sake of having romance incorporated with the plot. Though you brought up a point that I didn't consider; they really could just be misleading us.
The romance feels so odd.