NTT East now provides WiFi for tourists. NTT East operates in eastern part of Japan. Example: Tokyo, Hokkaido and Yokohama. Remember those days when we rent handphones in Japan? No more!
Where are the hotspots? You will see the stickers pasted on shop from.
Alternatively, you can also check the hotspots here before you go.
1)Using iOS or Android app. Download the app “NAVITIME for Japan Travel” app, provided by NAVITIME JAPAN and obtain the WiFi ID and password. http://flets.com/freewifi/step.html#app
2) Free WifiCards with WiFi ID and password from various location. Passport required. http://www.flets.com/freewifi/spot.html
The other cities do provide WiFi for touriset, but not by NTT East.
One final note though, do remember that you are on vacation, put that phone away.
It is Japan. Time to appreciate the lovely people, culture and surroundings and the loved ones with you.