Update: This bug has been fixed and a new release of Nihongo no Kana has been submitted to Apple for review. It should be available for download in a few days.
Some users reported a blocking bug with the new release of Nihongo no Kana 1.1, resulting in a blank screen at start. We are currently investigating this problem. Any information you can report (iOS version and device model, etc…) may help us find the right solution. Feel free to contact us at any time if you are experiencing this problem.