I would recommend to get a prepaid cell phone, since Japan is a strict country for use of sim-free cell phones. You might be able to get just a simcard(without buying phones) from cell-phone shop, but most likely, they don't sell just a sim card. And a big advantage for a prepaid cell-phone is that you don't have to make a contract with the phone company. The article below is about 9 months old. I think the current average price for a prepaid cell is about JPY5,000-7000. I remember I paid about JPY7-8000(USD8-90) for one about 4-5 years ago. It inclueded a simcard and cell-phone itself. (You may have to buy a charge card separately. ) http://answers.yahoo.com/question/index?qid=20100217123735AAetLUD http://mb.softbank.jp/en/prepaid_service/

Welcome to Japan. This is website of Narita Airport. http://www.narita-airport.jp/en/guide/service/list/svc_19_1.html There are many rental cell-phone company in airport. Please compair and choose your suitable service. If you come with frends and want to use like Walkie-ｔalkie, you can choose following servise, "Free of cherge"(1AM to 9PM). http://www.g-call.com/e/rental/dom/ryokin.php Enjoy your trip.

You need a prepaid. Japan is SIM free, almost. You can rent a Sim card when you arrive at the airport, but it isn't cheap and you must have a credit card. Or you buy the prepaid phone package. You can get the stylish one for about 18,000 yen at the airport, or a much cheaper one at Roppongi electrical store for about 4,000. I forget the name of that store.