I'm not certain if my info is current but I don't think you can get a contract without a residence in Japan. I got my current prepaid phone in 2010 from SoftBank but since my sister came with me (she's a resident) I don't remember if any visitor can walk in and buy a phone. I bought one easily in 2005 and when I ruined it later I found the rules had changed and they wouldn't sell one to me without my sister's assistance (in 2005). In 2010 my sister had to call around several shops before she found one that actually carried pre-paid phones. There were only 2 models available.
I took a look at your blog:
>_< You need help with your route. As you've already found the Japan Cycling Navigator website you should look at that more closely. It would be a real shame to skip the Shimanami Kaidou (connecting Honshuu and western Shikoku). Going around the south coast of Shikoku is probably good (I haven't done it but want to), the central north coast is so-so. You also seem to be going through an excessive amount of dreary urban concrete on Honshuu. Better to hop the train in places.
I would really recommend heading north from Toukyou to the Touhoku region. See the tsunami-hit area and do some volunteering. Here's my journal:http://www.crazyguyonabike.com/doc/?o=1 ... =8922&v=BE