Maybe this is of more use.
How to get a mobile phone:
Rental Phones
Renting is the most economical way for the average traveler to get a phone, and typically requires a picture ID and a credit card. Many companies have kiosks at the airports, while other companies will mail a phone to your hotel or to your home. You can return the phones at the airport or through the mail depending on the company.
The fees for rental phones vary and usually consist of the rental fee (typically 250-1000 yen per day) plus a usage fee (typically 70-200 yen per minute domestic outgoing, incoming calls are free). All of the companies at the airports have same day rentals, while some companies offer discounts for advanced reservations.
Prepaid Phones
Due to past criminal abuse of prepaid phones, phone sellers must now verify the identity and place of residence of their buyers. Typical proof can be in the form of a Japanese driver's license, a Japanese Passport, or an alien registration card. Some stores will accept foreign passports along with a hotel address as verification.
Prepaid phones start around 5000 yen. Credit, which is used for outgoing calls, email, internet, etc. depending on what features your phone supports, must be purchased in advance. With most companies, incoming calls are free and outgoing calling rates are comparable to those of rental phones.
Credit can be bought at cell phone stores and convenience stores and is typically valid for two months. Phone numbers remain active as long as you have valid credit in your account, but will expire after four months to a year without use.
Subscription Plans
With subscription plans you pay for your usage at the end of a monthly billing cycle as opposed to prepaid phones where you buy your usage before you use it. The phones themselves can be free although that typically requires a 2 year contract.
All the latest and most advanced phones are available with subscription plans and the selection of handsets is huge. Subscription plans are only available to residents and require an alien registration card and a Japanese bank account.
http://www.japan-guide.com/e/e2223.html