Apple added support for Japanese in iOS 5.1, but the roll out isn't going as smoothly as expected. According to a Kotaku report, Apple's voice assistant can apparently only handle simple and universal Japanese phrases. When it comes to complex phrases, Siri stumbles while its competitor Shabette Concier performs flawlessly. Shabette, a recently-launched voice service from wireless carrier NTT DoCoMo, is targeted specifically for Japanese customers and support
