I'm not sure what you are asking... as a tourist in order to obtain services for a device at a residency, you'll need a gaijin registration card. You can still get this card with only a tourist visa, however.
Celular technologies are not flat rate, but if your pocket pc supports some sort of a/b/g wireless you may be able to find a internet cafe... though I didn't see a lot of them, not nearly as often as I've seen them in other countries.