japanesse app should include
It would be very helpful for you to learn all the Joyo Kanji, but the basic 1,000 characters are sufficient to read about 90% of the kanji used in a newspaper (about 60% with 500 characters). Since children's books use less kanji, they would be a good resource to practice your reading.
By Namiko Abe, About.com Guide
Welcome to my free Japanese writing lessons. There are three types of scripts in Japanese: kanji, hiragana and katakana. The combination of all three is used for writing. Japanese characters are very different from those found in western alphabets. You might think it is hard to learn, but I think it is the most interesting and fun part of the Japanese language. Already confused? Don't worry; these free japanese lessons will help you to understand how to write Japanese, step by step.