Um, have you even read the comic? She has never once directly stated that she likes him. She doesn't like that he doesn't realize that she has feelings for him. Okay, so if he doesn't know, then the obvious solution is... apparently to never once correct him and just expect him to read your mind. Great.
It's a common trope that I dislike in romcoms. Spit it out, woman! Like the ending. She wants to get his deets, and he misunderstands. This is where a normal effing human being is like, "No, you misunderstood me, what I want is this" and he'll either be totally nonchalant and just be like, "Oh, ok" or get flustered. If he gets flustered and THEN acts like a doofus, then yes, he's dense.
But every time he asks her for more context, she goes full tsundere and he seems to just take it at face value. She's the issue in this relationship. Now, if she was throwing herself at him and acting like a character in a harem anime, then yes, that's dense. But expecting your crush to just magically understand you is absolute lunacy.