Japanese IME ?

No language preferences in iphone at this time.

iPhone input in English only in the current version.

For an example of a web app workaround for typing email in other languages, you can point the iPhone browser at this page:

http://pointatme.com/keyboards

In theory you could create the same kind of thing for typing Kana, though I suspect you would have a hard time finding space for all of them.

I'm dying for this as well.
Hopefully the fall update that's rumored to ship when Leopard ships will include this as well as other new features. There is no reason it can't include it.

iPhoneで日本語ができるじゃん!!

im on my iphone now and since the 1.1.1 update, i stumbled on a glitch.

I was searching for jp words on the dictionary site, www.sanseido.net and after two searches, an IME appeared above the keyboard. I thougt it was the keyboard responding to the website but i tested it on oricon and mixi. When i went to the yahoo US site it stopped. However wheb i opened a second safari window with the sanseido site to "initiate" the IME, it worked on yahoo as well.

There is some more info in this thread:

http://discussions.apple.com/message.jspa?messageID=5455545#5455545

I've already posted about this. Not your fault but amazing how other places have my work around and yet most people are still in the dark. Apple is not keen on this I think. However there is a way, in Safari only to have a Japanese/Asian keyboard:

Again my method for fool proof 100% Apple Inc., Safari Japanese input:

open safari

www.alc.co.jp
(you will see a long text input box, site is all Japanese but it is near the top)

tap select text box

tap-type: test

let tap go or tap the kanji button for translate

let page fully load

Then tap select text box, it will have the word "test" on it

Then your keyboard will come up but this time it has a rectangle above the slightly smaller keyboard.
tap-type: W

You'll see W, kana for watashi, kanji for watashi, select one of the options and it will hover then input the kanji/kana/w into the text box.

Then go to gOffice for iPhone and type a Japanese .doc then email it or go to your gmail account or anyonline account and type full Japanese emails to your hearts content. This will work for any site you go to directly page to page, site to site.

BUT pushing the home button to go to another app will cancel this keyboard.

However if you save the "test" result in your bookmarks then just reload, tap highlight the box and you have on Safari a full Japanese keyboard. It might work for other asian languages.