Nihongo no Kana 1.0.4 is now available on the App Store. Thank you for your feedback. We continue to improve Nihongo no Kana thanks to your recommendations.
New features and improvements for version 1.0.4:
The next major release should include iCloud synchronization support.
However, some users have reported us a bug that can occur during a Practice session and which forces the application to close itself. We are working on resolving quickly this problem and will publish an intermediairy bugfix release before the major next one.