they talk about this at the end of chapter four! i would say he got interested back in their first (technically his second) year when hanbin had no clue who he was and they spoke on that train ride after he helped hanbin find his wand. i think that’s what piqued hao’s interest, despite his own denials to himself and his steadfast belief that this confession would be no different than the rest, initially, and then hanbin won him over by doing exactly what he had done on the train: seeing him as no one else did, or at least seeing to the truth of him, beyond the rumors and his reputation and everything else that people seemed to want to be with him for. this is a pretty cobbled together summary haha but yes their conversation at the end of chapter four and then also perhaps their hogsmeade scene and astronomy tower scenes later on in hao’s pov will help shed light on how he sees hanbin!