Looks like more options are coming to users of mobile data in Japan. Via @Durf, I understand that the Nikkei reported today that US Amazon.com is entering the data SIM market in Japan. Service will work with Docomo phones and tablets, as well as overseas unlocked iPhones. This indicates that there should be both regular and micro SIMs on offer. Amazon will also be offering the Kindle in Japan from this summer.
The SIMs will be available through the amazon website. It's not clear if this indicates only the US or also the Japanese site. Whether this is a good option for travelers to Japan depends on the activation and surcharge requirements.
Japan Communications Inc, who sells the b-mobile and Aeon SIMs, is reportedly the MVNE, though JCI's comment was essentially "no comment" (PDF). This will be an LTE service that will support Docomo LTE devices and any 3G device that supports UMTS-2100 MHz, aka Band I. (See this frequency comparison chart.) Non-Docomo devices will have to be unlocked.
The price is reported as ¥1,980/500 MB.
Other than the above, not much is known. This is just SPECULATION, but at that price point, I'd expect that:
- When used in a 3G device, speed and latency will be comparable to the b-mobile 1GB Flat Rate or Aeon Plan C. (Not as fast and responsive as the b-mobile Fair.)
- When used with Docomo LTE devices, speed will be quite high and latency quite low, both of which are good.
- A charge will be valid for 30 days. [This was correct.]
- Streaming/VoIP/Skype/YouTube will be allowed. [This was correct.]
- There will probably not be an additional surcharge for the SIM card. [This was incorrect, SIM costs ~ ¥3,000 up front.]
- The SIM will expire after a certain time with no charge. [This was correct, but charges are monthly and recurring. Canceling service kills the SIM.]
- The SIMs will be produced in Japan and therefore shipped only to domestic Japanese addresses. [This was correct.]