Nevermind, found them myself, thanks to the extra files.
Shiraki Aeka's Seiyuu - Yuzuki Kaname (Apparently, the voice she uses for Aeka is her IRL SPEAKING VOICE OH MY FUCKING GOD X3 )
Mizuki Kanso's Seiyuu - Ishiki Hikaru (Holy shit, listening to her interview in the extras, she sounds fucking crazy IRL. Apparently, her IRL speaking voice is equivalent to Mizuki when she's drunk or high.)
Cat Sidhe Nekoko's Seiyuu - Chiyatani Yasura (Surprisingly enough, she's the most normal sounding one. Her laughs are rather throaty, though.)
Too bad I can't find pictures of ANY of them. Yasura-chan herself is apparently completely no-name. Like, this is the only seiyuu work she's done EVER. A shame, really.
Also, to anybody who can translate kanji, if you could do so to the attached picture, I would love you forever. It's the lyrics of a parody OP for the game.