Ditzy Genius: She's not very well-versed in the outside world but is at the top of her class.
Stalker with a Crush: Haruka veers dangerously towards this trope during the first half of the game, even using her influence with the Principal to be allowed near Kazushi when she shouldn't. Actually subverted: Haruka has been stalking Kazushi because the Principal ordered her to... for her own dark reasons.
Covert Pervert: For someone who claims not to be interested in sex Mizuki is very knowledgeable in the subject.
Tsundere: Albeit a very light one ("I'm not smiling at you!")
Everyone Can See It: During Ran's route, everyone else is surprised when they hear that she and Kazushi aren't already dating.
Money Fetish: Ran's mind seems to be absolutely transfixed in money, so much as to actually disregard her own safety to rescue a burning wallet. There's, of course, a reason for that, though it's pretty dumb.
Sexy Backless Outfit: Ran in her normal clothes, she even, nonchalantly, points this out when the guys go crazy over someone's bra going missing.
The Tease: That one time when the guys (and Ran) peeked on her changing.
Covert Pervert: According to Sakura, Rin wears pretty raunchy lingerie. In Eiden Fantasia you actually discover that she does, but she's not that much of a pervert, even if her route starts with her having some pretty perverted dreams and she really lets herself loose during the True End.
Beware the Nice Ones: The role of the Principal varies greatly from route to route. In Mei's route, she's mildly obstructive with traces of a dark past. In Haruka's route she starts pretty evil, but eventually becomes a tragic figure. Aside from some details, she's pretty much absent of Ran's route, but on Mizuki's... hoo boy. She pretty much enters full-blown Big Bad mode, blinking in and out of existence, launching people into the air and trying to hack Kazushi's legs with an axe just to prove a point. As noted on Lighter and Softer, she's not that bad in Eiden Fantasia.