Picrumb knows it is extremely difficult to use your phone online in Japan and not worth making it online by paying a lot for a short period of time during your stay. But do not worry. There are certain places you can connect your phone to WIFI for free. The best Wifi spot might be Starbucks because they exist almost every block around the corner in the center of the city.
The map is a Wifi finder that shows Starbucks Free Wifi hotspots in most of the major cities in Tokyo including Asakusa, Akihabara, Harajuku, Roppongi, Shibuya, Shinjuku, Tsukiji, and Tokyo Station. In those areas, you can also find the Best Local Restraurants chosen by the most influential Japanese restaurant site which is used by 48 million locals monthly.
You need to access to the link below to fill in your email address and password. Then press "Submit". https://service.wi2.ne.jp/wi2net/SbjReg/2/?locale=en
You will receive the "Complete Registration" email to the address you just registered.
If you are doing this registration at home, you can just open your email you received from Starbucks and confirm your account information by clicking the link. But if you are currently at Starbucks trying to register, you need to either go back to your hotel to get Wifi access or go to internet café to receive your email from Starbucks. It's ironic that you need Wifi access to receive confirmation email for registering Wifi, but once you confirm, you will have full access to free Wifi service!
Make sure you do this within 24 hours. Otherwise the link you received in your email will be expired. For more information about how to sign up, you can click here. http://starbucks.wi2.co.jp/pc/menu2_en.html