If you're keen on stuffing yourself with casual Japanese food before going back to the states, I'd recommend asking either at the Narita Hilton (that might be one of the hotels with the free shuttle) or in a downtown hotel (for the public bus) that goes to the Aeon Mall. If you take a look at that link, the marigold-colored road with the number 408 on it, keep shifting the map to the "right." Many of those establishments on 408 are restaurants- kaitenzushi, tonkatsu, shabu shabu, ramen- cheap, family-friendly types of restaurants. All are within a 10-15 minute walk of the Aeon mall bus stop. I wish a copy of this road existed in the NYC area...

If you have wanderlust like me, you could walk from the JR Narita train station to the Aeon mall in less than thirty minutes. The info booth at that station can give you clear directions, along with a map.