NTT East Free Wifi Card
At the Narita Airport you can get NTT free Wifi card.
Seems only available at Terminal 2 from April.
The card is only good in NTT East area which is Tokyo and North including Hokkaido.
NTT is a big telecommunication company and you can use their WiFi spots for free.
Also in Tokyo, you can pick up the card at some shops that is marked with blue dot in this map.
You cannot resister in the shops so have to resister beforehand.
Please sign up here beforehand.
Not the all shops have free WiFi but over 800 shops has it.
If you want to check specific location you can do so at here.