I used
http://www.jcrcorp.com/
in 2001 and thought very highly of them. I, however, took advantage of the free incoming calls. I used a callback system which provided significantly cheaper outbound calls than the rental company offered.
Also, look at voicestick.com. They will give you a free US or UK number which you can forward to a Japanese cellphone for 3 cents or 11 cents a minute depending on the carrier. If you use foreign mobiles rather than roaming, voicestick is handy tool for your tool box.
Originally Posted by Sigh
A year ago, before I knew about FT, I traveled to Japan and rented a cellphone from G-Call after scouring the Internet for options. As I recall, I did not even reserve a phone, but elected to just show up at their kiosk (administered by another company, as I recall). Everything went without a hitch. I rented and returned the phone at NRT.
Be sure to return the phone before you check in for the flight because there is no way to return the phone after you cleared security and I believe you must proceed directly to security from check-in.
OK, I messed up. I got through security then realized I hadn't returned the phone. I phoned them from the NRT Red Carpet Club and they said to mail it back from the States. Instead, I found a fabulous RCC agent who had the run of the airport and took the phone saying "I'll be back in a minute". Well, it was more like 15, but he returned with a receipt for the phone from G-Call.
The G-Call website is
http://www.g-call.com/e/rental/dom/rental.php
I have no affiliation with the company whatsoever, just thrilled with their really cheap rates and really great service.
A hint for asking for help in Japan: While many Japanese have taken English in school, I found that quite often they could not understand what I was sayong, nor could I understand them. However, they could read and write English. So, if you are not understanding each other at a Japanese business, just write notes back and forth.
Happy travelling!