After news that the latest iPhone 2.0 beta firmware (due in June) had incorporated Chinese handwriting recognition, there were many readers who were interested to see the input options for Japanese language. Handwriting recognition is not available for the Japanese language in the latest beta.
Instead there is the standard keyboard:
As well as a Kana international keyboard:
These images are from the latest beta (5A258f) iPhone 2.0 that is available to developers. The final version will be released to consumers in June.