I dont think that prejudice works like that at all, not in real life at least. There is usually a specific fear attached to it.
In any case this manga is very thematically dense: its a novel adaptation?
Yeah, this is ending. Lesbian Karin was teased at chapter 1, and her gimmick of not being interested in the MC could be an entired arc on its own. But instead she came and went in a couple of pages.