Remember the two silluoetted characters? Both of them have been revealed (though their names and information are still hidden).
http://www.yetigame.jp/w/chara11.html
http://www.yetigame.jp/w/chara12.html
Ai Shimizu's character looks like a younger version of Mutsuki from I/O, IMO.
Momoko Ohara's character... can't get that much off of her, but I can see why she has the voice she does- she does seem rather tomboyish looking.