Rob Hawkins reports:
"At Narita airport for at least the last year, I've been able to connect to their internet without having any ISP. The network is something like Narita Airport Free WIFI
"When you load a webpage it will redirect you to a page in Japanese, then you click "English", then Register, enter an email address, and then you are given access. This works with any phone, tablet, or laptop."
Here's the official info from the Narita Airport Guide: Narita Guide: Internet
There is a small internet access point on the main road in Narita (Omote-san-do - the one that leads from the city center down to the temple). This is on the right side as you are going down, not far from the "Flyer's Lounge".