Allright, devil's advocate here because I'm seeing a worrying amount of heat in the chat.
You all need to remember that he continuously told Chiko that he liked her voice and that he had a thing for voices, yet she never mentioned anything about her voice being fake. The whole voice thing has always been a big deal for him and she has been lying, if by omission, to him about hers. See the following examples:
[ul]-You have a thing for big boobs and the girl that has been getting close to you turns out to have been wearing pads all along
-This fundamentalist christian has been seeing his christian girlfriend for almost a year and discovers that his girlfriend was jewish and pretended to be christian
-Sir Mix a Lot finds out that his newest girl has been using inflatable buttocks in order to impress him[/ul]
Now, while it's not a capital crime (or a crime at all for that matter) it does present a roadblock to the whole relationship. Nevertheless, while he started by being attracted to her voice, we have seen him get attached to all her other quirks little by little and falling more and more in love with her; he's not outright says he doesn't like her anymore, he's having an identity crisis because the girl he has liked for this long turns out to have been hiding something that was quite relevant to the whole "relationship" (because we need to remember, they're not dating or anything yet), they still have a solid friendship due to all the time and quirks they've been through together after all this time and there's no way he will send her away just for this.
In the end, this can go one of two ways: either he can't deal with it and will stop pursuing Chiko, but still be with her and protect her because he values what they currently have as a good frienship, or he will decide that he likes her after all in spite of her having no voice and realize that him liking voices is just that, a fetish.
My uncle used to say that we like people for their qualities but we love them for their defects. - Hellboy