There is a free Wi-Fi service for tourists going to east Japan provided by NTT East this year. You can use this free Wi-Fi service for 14 days. This might be a good thing to consider adding in your trip plan to Japan. Please see the dates of the card distribution below:
2nd, 3rd, 6th, 7th, 10th, 11th, 14th, 15th, 18th, 19th, 22nd, 23rd, 26th, 27th, and 30th.
1st, 4th, 5th, 8th, 9th, 12th, 13th, 16th, 17th, 20th, 21st, 24th, 25th, 28th, and 29th.
If you are arriving at Narita Airport first, you can obtain the Wi-Fi card near Zone A, International Arrival Gate, 1/F, Terminal 2, Narita Airport. Please note that the business hours (only when Gate A is open) are 12:00-20:00 and there may not staff around during the lunch time.
For other places that distributes the free Wi-Fi cards and where you can use them can be found here.
What you need to do after arriving in Japan
1. Present your passport at the distribution places mentioned above to obtain this card.
2. Look for the places with the logo shown below:
Fig. 1- Places with the logo to use with the free Wi-Fi card 
Source:  http://flets.com/freewifi/service.html