For the longest time, Misaki doesn't tell anyone that she's in love with Usui (she doesn't even admit it to herself). He's an alien, she tells herself instead, a pervert, an annoying stalker she can't ever get rid of. For a while, her repeated excuses work as a ward (she almost brainwashes herself), but it's a cheap one easily broken whenever Usui smiles, truly smiles, at her, causing her to blush all the way to her ears.
What she loves most about him is perhaps his patience with her (hah, patience, she never would have thought that in the beginning). He knows her feelings even better than she knows them, so he also knows she's not ready.
For the longest time, Misaki doesn't tell anyone her feelings, and Usui doesn't rush her.