Charging the iPhone in Japan

See if you can find it via the international store option.
However I clicked Japan and it said the Store is being updated try again later.

http://store.apple.com/Catalog/US/Images/intlstoreroutingpage.html?cid=AOSA10000 022132

Just got back from Japan,

I was able to use my original plug in the hotels.

You can also use a plug adapter for the AC adapter that came with your iPhone. The little AC adapter runs on 100-240 V, 50/60 Hz, so it works nearly everywhere in the world, provided you have an adapter so the plug fits.

You can get the appropriate plug adapter at a Radio Shack or a travel store.

The Japan version of the iPhone AC adapter is available on the Japan Apple Online Store, but purchases from that section of the Store must be shipped to postal addresses +in Japan+, so that won't help you much.

Bingo - George is correct.

The outlets in Japan are the same plug as in the US, but at 100 V instead of 110 V:

http://www.kropla.com/!ab.htm

Since the adapter takes 100 V as well, you are all set!

Our regular AC plugs work fine in Japan as long as they are not 3 prong.

The regular US 2 prong plug will work in Japan.

Seems like you are living in California. So for your information, U.S.A and Japan uses the same 110 V cord with the 2 prongs so you can just take the charger to Japan and use it.