If you stay in Tokyo, you will see a lot of Japanese characters you may not be able to read. Except for the airports, train stations and other public places, translated information is lacking in many places or situations in Japan. Here is a good solution for that.
Google Translate by Google
* Type to translate 90 languages
* Use your camera to translate text instantly in 26 languages
* Two-way automatic speech translation in 40 languages
* Draw with your finger as a keyboard alternative
* Star and save translations for future reference
* Take pictures of text for higher-quality translations or for languages not supported by instant camera translation