4G data enabled device for 3 months

greetings all, and thanks for providing such insightful and useful information on these forums. This summer I will return to Japan for a 3 month internship. I found that in my previous times in Japan the most useful tool I had was a data enabled device which allowed me to use my GPS and maps feature, and internet. I also liked to have data connectivity on the phone, but did not need voice at all. I know that there are prepaid Sims which I have used in the past from b-mobile, however, they were always 3G, relatively expensive for little amounts of data, and always kept my downloads at horrible slower speeds. This summer I was wondering if there were any resources available to somebody who was staying for an extended stay to get a 4G enabled device. I was wondering if it would even be possible to buy perhaps a tablet on Amazon Japan and somehow acquire a SIM card. My phone is about a year old so I am due for an upgrade but I know that United States phones especially those on Verizon will not work on the 4G network in Japan. So my final question is this --is there a SIM card available for extended stay which is reasonably priced for which I can stick in a tablet or mobile phone that I can get in Japan?or is there another way to go about this? Thanks very much.

http://service.ocn.ne.jp/mobile/one/charge/

leased DOCOMO 3G/LTE ranges of data usage plan to suit your usage, all , ranging frpm 980yen(50mb/day) to 1944yen(8GB/mth at 500kpbs )

require credit card and local address/contact, can cancel anytime or change plan(once per month)

Any way to also get on the monthly wi2?

ocnmobileone, thank you very much.
will the mobile one sim work in any mifi device? If i buy an unlocked Huawei E5220s-6 will it work in that?

answered here:

http://www.japan-guide.com/forum/quereadisplay.html?0+113262