木の根ペンション (Kinone pension) is a very special hotel, right in the middle of Narita Airport:
It seems to have no website and no phone number, it can't be found on booking websites. It is on Google Maps though. This Excite article says it costs 1000 yen per night (yes very cheap), the article talks about a tunnel to go there without giving precise directions, and instructs readers to ignore the "No entrance" signs.
QUESTION: How can I walk to this hotel from a Narita airport terminal?
Anything special I should be aware of if I want to stay there?
This Yahoo Answers page asks the exact same question, but the answers don't give directions, only talking about the heavy police surveillance.