Matt stopped by Oni Central's forum to (among other things) answer the question of whether or not Konoko has a voice.

Yes, although in the builds I've seen so far she's only had placeholder sounds, which at one point included a pitch-shifted Joseph Staten and (in a cutscene just before a battle) the Let's Get Ready To Rumble guy.

Her real voice will be provided by an actress named Amanda who has done a lot of anime voiceover work. There are some funny anecdotes I could tell about the recording sessions for Konoko's voice but this is a family page. At least I think it is.

Pico suggests elsewhere on the forum that Amanda could be the major Anime voice actress Amanda Winn-Lee, who (among other things) did Rei's voice in the dubbed version of Neon Genesis Evangelion.

Here's the thread Matt chipped in on.