Here's a game I worked on last year (characters, items, backgrounds, well.. pretty much everything except all the User Interface thing) It's called "Japanese Learning" (by Tokkun Studio), released on June 7th, and it's available on iPhone and iPad on the apple store (looks like there's no android version for now).
haha, it's a cute little app ^_^ I don't need it, because I'm actually already studying with textbooks and everything and possibly starting classes soon, but it looks like a great app for lots of people! The character designs are so cute too!