I don't know. I can't think of any part of Tokyo that has such old buildings in such a large concentration as Kawagoe does. So many of them were destroyed during World War II. But you're right in saying that the northern part of Tokyo is less international-looking than the southern part, although only Yanaka has a significant number of old buildings.

For a view of working class Tokyo, take the last remaining streetcar line from Otsuka (on the Yamanote line) or Waseda (on the Tozai subway line) to Minowa.

I had been told that the island of Tsukudajima in Tokyo Bay retained some of the flavor of yesterday, but evidently I saw it too late. The builders of high rises have already arrived. It does, however, seem like a cohesive community and has a couple of side streets that have so far escaped the developers.

Otherwise, one of my favorite activities in Tokyo is to pick one of the major "named" streets, such as Waseda-doori or Eitai-doori or Kasuga-doori and walk as much of its length as I can. I always find something of interest. I forget which such walk it was, but I once encountered a neighborhood of shops devoted to selling every conceivable kind of brush, from paintbrushes to floor-sweeping brushes.