Rick,

There are two (possibly even more as of this writing) GSM carriers in Japan. They are NTT DoCoMo, Inc and Vodafone K.K. (J-Phone.

He would technically not need another phone or SIM to be able to make and recieve calls...BUT it will cost him much more per minute (whatever Cingular charges for world rates).

I would suggest calling cingular and finding out about the feature. You might have to activate it (usually free) and they will tell you how much the minute rate will be. I traveled to Dominican Republic and Russia with my T-Mobile phone and had no problems.

If you ever need a GSM enabled phone, please check out my store:

http://www.towerofsavings.com/cgi-bin/ISStore/store?action=view&RO=9w3bijycsk&dep=electronics&cat=59&sub_cat=334

Good Luck!