I just spent some time in Japan in November 2012 and struggled for the first day trying to find out how to either use my existing Canadian Android Nexus S cell phone or rent a temporary one. I thought I could simply buy a temporary SIM card like I can in the USA, but the internet seems to say this is not possible. I did a lot Google research and it looked like the only option that made sense was to rent a (no data, no long distance) phone from a company like Rentafone Japan or Cellular Abroad. Lame! So then I spent hours in Shibuya exploring options at various telecom stores for renting a phone and it was a total pain in the ass. Luckily, I met a friendly German man who explained that he bought a SIM card in Akihabara, and that as long as my phone was unlocked and worked on 3G, which is the case, I could do the same.
So then I realized for the first time that Google is unreliable for at least information in Japan. I realized I could buy SIM cards at BIC Camera! But just so you all know, you can’t expect to type “BIC Camera” into Google Maps and find the stores. You actually have to use the Japanese name, or URL www.biccamera.com:
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I bought a 3GB SIM card that expires in 3 weeks, which was plenty for me. It cost me $5,800 YEN, or about $73 CAD, which was a deal, especially considering the convenience of using my regular phone with all my apps. For free text messages, I used Google Voice (see how to get Google Voice here) and for free phone and video calls I used either Google Chat or Skype.