Buying a cell phone in Japan

I'll be staying in Hokkaido for two months this summer. I plan on getting a cell phone, and I will most likely be getting a prepaid one. I heard that if you're going to get a contract, you need to have an alien registration card. Do I need to show anything to get a prepaid phone? I also heard that people under 20 years old can't get a cell phone by themselves in Japan. Does this also apply to prepaid phones (I am 19 years old)? Any other restrictions I may have?

Will be travelling to Japan soon and looking to purchase a Nokia n95 Cell phone. Where is the nearest outlet to Narita Airport.

Thanks!

Buying any type (contract or prepaid) will require a residence or alien registration card.

AU prepaid: http://www.au.kddi.com/english/customer/what/index.html

Softbank prepaid:
http://mb.softbank.jp/mb/en/prepaid/purchase/registration.ht...

hi

there are Nokia store in Narita Airport terminal 1&2.
Price for N95 is around 84000yen