Jouyoku, Ai: Ai as a whole person prefers sexy evening dresses and extremely sensible pantsuits and tiny reading glasses. She also somehow manages to wear and enjoy heels. Because well. Demon. Fuck your laws of physics.

Normal Ai prefered a sexy, but without being slutty-risque look. Mini-Skirts. Tops that expose a bit of the belly. Classy heels.

Human Ai currently is kind of... frumpy. Clothes that hide her curves. Loose sweaters, T-Shirts, and pants.

Demon Ai has her more regular Succubus self, but while keeping to a sensible but sexy look, well. I get this air of sleaze to her. So.

Adam Van Der Aart:
Good question. I see him preferring maroon and magenta. Dark reds. Bloody colors. Probably wears leather jackets.

Jasumi: Purple/Red sweaters. Mom jeans. She and Shiyoko share oddly similar fashion senses.

Yamamoto, Suzume: Suzume prefers jeans/shorts/slacks. Sneakers. And red/orange/yellow/brown sweaters. However, her current biology would make it much easier if uh. She was wearing very tight clothes around the hips/waist, nothing below the knee, and went topless. It's a massive frustration point for her.

Moeko: Rich vapid bimbo clothes is the only thing that comes to mind.

Yamimaru: Pretty much anything his PB would wear except tuxedos, 'cuz those are lame.