Absolutely amazing. Astounding. – Human Japanese Review

I would recommend this application to any and every person who is looking to get in to the study of the Japanese language. Not only does it cover grammar, but also vocabulary. The intermediate version goes in to kanji as well, if my memory serves correctly, thus giving you the three keys to learning the Japanese language. You will eventually need more sources to continue to learn, but this app is VERY extensive.
Review by wanwandrew on Human Japanese.