Reading the 11 pages of the discussion, it's amusing how many people didn't get the character of Kurokawa. At least at first. I surmise that, now, they must be understanding her a little better... right?
I mean, it's not that hard to get. The hetero version of the trope is as old as literature. You know what I'm talking about? The story where the female lead claims to hate this guy who is super handsome, cool, rich, popular and has dozens of sexy women at his feet... she hates him, hates, hates, totally hates... then one day he confesses his love to her and asks her to marry him, and she fly-glomps him and starts kissing him. Yeah, cuz she didn't really hate him, what she hated was the fact that he didn't pay attention to her; once that's fixed, all's well in the world and they can start making babies. What we have here in "Useless Princesses" is a variant of this old trope on a yuri note. Kurokawa doesn't really hate those haughty, beautiful, arrogant, sexy, snobby alpha bitch princesses. She loves them and puppy-adores them and crushes on them like crazy. What she hates about them is that they won't return her feelings! That's why she has these (seemingly) contradictory sentiments of "I hate her, she's a bully!" and "I want to protect her shining smile!"
It seems quite clear to me that Kurokawa is a little lesbian in the making, who may or may not completely understand herself yet. Even her love of BL/yaoi fits in the picture. (It's a genre for girls by girls, and the characters are usually projections of female fantasies, to a point that it has been described as "lesbian fantasies in male drag" by some researchers...)
The one character I myself find kind of puzzling is Fujishiro. Okay, so being dumped by her trophy boyfriend was a big shock, sure... and being comforted by Kurokawa was nice, yeah... but going from there to "I'm-a dumping all my old friends and I'm-a relinquishing my queen bee position and from now on I'll live with Kurokawa in a cozy little hole in a quiet corner of the classroom, just the two of us, forevah!" is, like, kinda too big of a leap... obviously there's something in her psychology that escapes me...