I agree with railroad tycoon, check out the many posts in the Japan Forum on this topic.

It really depends on when your <24 hours is during the day. Do you intend to check into a hotel and sleep part of the time or just do an all-nighter and stay up the whole time? That 24- hours is actually less than 21 hours when you subtract an hour or so to exit immigration, change some money and get on a train and another 2 hours back at the airport in advance of your onward flight. If you will have some daytime but will be sleeping the night before your departure, I strongly suggest that you go with your instincts and stay in Narita. There are lots of very reasonable hotels, several decent restaurants, a very nice temple and garden area and pretty decent shopping street. Narita is probably not a good choice for a multi-day stay, but for 12-14 hours plus a hotel night it is not bad. And you won't have any time pressures getting back to the airport.

Going into Tokyo you have to subtract another 2.5 +/- hours for transportation and navigating stations, so would have 10-12 hours or so to actually see anything. If you do this, I agree that you should consider seeing some of the more modern areas of Tokyo to compliment the older parts you have already seen. Ginza, the Imperial Palace area, Shibuya or Shinjuku are worth a visit. Depending on what day you are there, Harajuku can be fun but most days is just a pain. There are lots of choices for a full day.

I'm getting older and slowing down, so in similar circumstances, I'd love a nice relaxing day in and around Narita, a couple of good Japanese meals and an easy, rested return to the airport for another long flight. YMMV.

Join us in the Japan Forum and check out the threads.

JR