[Sangetsu]

If you have AT&T, you can get an international plan which will allow you to use your phone while in Japan. The only drawback is that you need to have a later-model 3G phone. I used an AT&T tilt on a visit a couple of years ago and had no troubles. AT&T is partnered with the Docomo network, so that's the carrier you will use when roaming here.

When I use my Docomo phone in America, the phone says "Cingular" (I thought the name Cingular had stopped being used a few years ago), but the phone works well enough.