It’s really hard to get on the internet in Japan. Yes, you read that right - in the most advanced technological country in the world getting on the internet is not easy.
There are a ton of hotspots everywhere but you can’t use them, unless you have a cell phone contract with a Japanese provider like WiMax, Au and Softbank. If Japanese buy phones tend to be SIM locked and tied to a 2 year contract.
For travellers, there’s quite some options.
The first one is a system called Pocket WiFi provided by a company called Global Advanced Communications. Basically you rent a device that emits a WiFi signal. Then you can use this to connect your device to the WiFi hotspot. The device makes use of the cellular network (3G) so the speeds are not actual WiFi speeds. The cost is about ¥1000 a day.
My solution was to get a So-net SIM (So-net is a daughter company of Sony). The SIM cost me 5000 yen for 60 days of usage and just a measly 500Mb. I recharged for ¥3000 to get another Gigabyte worth of data. If you own an iPhone you will probably need to install a network profile to your phone. Instructions are provided when you buy the SIM.
Getting the SIM
You can get a SIM at the Book Off store near Shinjuku Station. To get there take the west exit and look for a glass-covered building across the Keio department store. It’s not very obvious so here is a picture:
(The address is: 4F-6F 110Bldg, 1-10-2 Nishishinjuku, Shinjuku-ku, Tokyo)
Some people have reported luck with a travel SIM called B-mobile. It should be noted that it doesn’t work with CDMA phones - only with GSM phones — so make sure to look up your type of phone before you buy.