Yuika is absolutely chaotic and is by far my favorite character in this manga. Honestly, with how random and chaotic she can be, I wouldn't be surprised if she suddenly held the school hostage while driving a military tank through its hallways just because they stopped selling croquettes in the cafeteria or something.
Just a side note: I do not condone driving tanks through school corridors, especially while holding the school hostage using the before mentioned tank.
...
Also, Nabi is a 100% bottom.
Coincidentally, Kaori also seems like a bottom.
It's scary that Yuika, the loli airhead, actually seems like she would be a very powerful top in any relationship. She certainly gets things done her way with efficiency, the creation of the club being the best example.