http://www.sleepinginairports.net/asia/tokyo.htm
from one of the 'sleeper' at Narita:
narita airport is this giant shell shaped thing that has a cool train. the seats are the ones that don't have arms on them. they are very well padded, however the floor is even more comfortable. also, there is a secure and free area where u can leave your baggage. terminal 'b' is easier to sleep in. they have good free tv sets everywhere, and it is generally quiet. the food is overpriced and disgusting, as is the beer (watered down of course) they serve. the bathrooms are nightmares, though. the women cleaners enter at any time and enjoy watching you urinate. "