Mobile service in Japan

I am looking for data service(preferably unlimited ones) with domestic call for my iPhone 4s & my partner iPhone 5. Could any kind soul recommend us the cheapest way to get it?

I am thinking of pupuru sim card service but they don't seems to have service for iPhone 5.
http://www.pupuru.com/en/service/campaign/sim.html

Appreciate those who have been to Japan to give me some advice. Thanks a brunch in advance!

Are you living or travelling?

We will be traveling 6 days in total for holiday.

You can rent a data+voice sim for each of your phones but it is extremely expensive.

http://www.softbank-rental.jp/e/rental-plan-ib03.php

Instead, I'd look into getting rental or prepaid voice sims and then rent a pocket wifi device for mobile internet. Here are a few providers:

http://www.bmobile.ne.jp/english/14days.html
http://jcrcorp.com/index.html
http://www.globaladvancedcomm.com/index.html
http://www.narita-airport.jp/en/guide/service/list/svc_19.html#t1