Traveling to Japan? Will you need a means of communication? Prepare your pocket if you are up to rent a phone, a SIM card or a Data card in Japan. Most providers give you different choices for rental devices, but be careful because prices from one to another might vary a lot. Please read carefully the following information and then check all the links. Prices can vary from one another, and through time as well.

Do you want to rent a 3G SIM card in Japan?

If you have an iPhone, or a NOKIA compatible with Japanese WCDMA2100 technology, then you are able to rent it. (Sorry, Android seems too new at this moment). Though you have some providers who give you the possibility to rent it, using Softbank might be one of the best choices.

http://www.softbank-rental.jp/en/phones/sim3g.php

Though renting might be cheap (105 yen a day), using it can turn your bill a nightmare.
Check the rates here

You can apply for it directly from your sofa at home. Get it online, and be ready to pick it up when you arrive at the airport. If you aren’t so sure yet about which provider you would like to use, just spend some extra time at the airport to rent your 3G SIM card. Note that you won’t be able to rent a 3G SIM card anywhere else.

What if I want to use my own phone?

If your phone uses a 3G GSM SIM card you will be able to use this option. You can rent just the handset and use the GSM SIM card. But remember that you must check your roaming agreements with Softbank (vodafone) prior to come to Japan.
http://www.softbank-rental.jp/en/phones/roaming.php

What if my phone has nothing of the above?

Then your only choice is to rent a Japanese phone. You can try the following services:
Softbank (quite cheap at the moment)
Pururu (with a special offer for 30 days)
E-phone
G-Call
Jal ABC

I also need a Data Card!

If you want to use internet wherever you go, to rent a Data Card for your Mac or PC might be a good idea. The most popular is called e-mobile.
The following companies offer data card services:

Pururu
E-phone
G-Call
Jal ABC

If you check the rates, Pururu has the best rental fees at the moment. But remember that this can change at any time. So please check all providers before flying to Japan.

What about a pocket wifi?

Unfortunately, at the moment, it seems that providers are not offering that option.

Where can I rent it?

At the Airport. You can check the list of providers in Narita International Airport here:

http://www.narita-airport.jp/en/guide/service/list/svc_19.html

Providers only have rent options at the Airport, so once you exit it, you’ve lost all opportunities to rent a phone, 3G SIM card, or Data Card. Unless, that is, you go back to the airport just for that.

UPDATE Nov. 3 2010: Read Visiting Japan? Mobile Phone and Data Plans to Keep You Connected