Originally Posted by
njxbean
you defintely have enough time to pop into Tokyo. The tour might be cutting it close if there is a delay. But at last you have time to pop in, wander, see a few sights and eat some sushi or ramen!
However, since Tokyo is a big and spatially disorganized city (think Los Angeles), you should probably read up on it and decide which area you want to end up in.
Most Narita Express runs land you at Tokyo Station (generic international business district) or Shinagawa (a fairly boring area). If you can catch one going to Shinjuku or Shibuya, they are major entertainment districts, although Shibuya is more trendy and Shinjuku, once the place to be, is a bit passé.
Another option, and probably the best one for a quick trip, is the Keisei Skyliner, which takes only 45 minutes to Ueno Station, a more interesting area, and runs every 20 minutes. Ueno has a park with museums (I like the Sh*tamachi Museum of prewar city life) and a zoo and is only two subway stops from Asakusa, home of Sensoji Temple and one of the more traditional-looking areas.