The term "Municipality" is quite unambiguous. NRT is in Narita City. That's the municipality. The city lines are very clearly drawn on the map.

Therefore, if you want to visit Tokyo or Yokohama on a shore pass, you're best advised to tell the immigration folks that you plan to stay in Narita City.

Others have pointed out that the immigration officials at the airport have some flexibility to interpret these guidelines, but it's wise to present such a request calmly and with humility and courtesy. (Weeping is not actually required, and I doubt it would help, although I can't say that I've actually tried it).