Possible to purchase pay-as-you go sim card in Japan for use on unlocked US iPhone?

[crunchyfeet]

It looks like there are some users on here who are currently living in Japan so I thought someone on here might be able to help me. I lived in Japan for a year about 4 years ago, and I will be returning for a month-long trip this April. When I previously lived in Japan, I was told that the only way to get a cell phone was if you had a gaijin card. I was not aware of any pay-as-you go plans at the time. I'd like to be able to use my unlocked iPhone on my trip with a Japanese pay-as-you go sim card instead of getting raped by ATT's international plan. Is this possible in Japan today? What is my best option for using my iPhone on a month long trip to Tokyo?

[Forgiatura]

I'm very much interested in knowing this as well! Also, information on pricing using pay as you go cards in Japan would be appreciated.

Thanks

[lamina]

I'm waiting at the airport in Incheon, South Korea, and thought I'd research this myself. I'll see if I can find a prepaid sim service in Fukuoka. I'll only be there for a few days though. I'll let you all know.