US iPhone on Japanese Carrier

Greetings-

I have a friend who will be studying abroad in Japan next semester at Kansai Gaidai University. I have an iPhone 3GS that has been unlocked from AT&T, and I'm working on setting her up with Google Voice and Talkatone so she can communicate with her friends back in the US via this service (uses mobile data to turn a Google Voice line into a voice over IP service). I'd also like for her to have a Japanese number so she can call and communicate with people there. Is it possible to get her a SIM with SoftBank or another carrier that will come with both a good amount of mobile data as well as local calling capabilities for time time she is there (about 4 months)? Do you have any advice? I would like to be able to give her some good information on this and have her set up with everything I can before she leaves.

Thank you in advance!

Is it possible to get her a SIM with SoftBank or another carrier that will come with both a good amount of mobile data as well as local calling capabilities for time time she is there (about 4 months)?

It would be easiest to get a sim via bmobile. However, it's gonna run roughly 7000 yen/month for voice and data. It can be a lot cheaper if you don't need the voice part, or can make do with a separate prepaid phone to handle voice.

http://www.bmobile.ne.jp/lineup.html

Thank you very much for her response. I will present these options to her. She is, as most college students are, on a pretty tight budget, but 7000 yen/month may be possible depending on how many scholarships for study she gets.

Thank you once again for your advice.