I don't think it's really the narrow streets that make Japan's town planning efficient. It's especially the mixed use and the fact that people can go shopping on foot from the home. But that is also true where I live in Belgium. There are even more shops than where I used to live in Central Tokyo: several supermarkets, bakeries, dozens of restaurants, clothes shops, etc. — all within 10 minutes walk from where I live. And that's in the green suburbs, not in the city centre. All the streets in my neighborhood are slow two lanes (one in each direction), but with tree-lined pavements for pedestrians on the side as well as bicycle lanes in some places (not enough though). This means that cars drive slowly, but are also well separated from pedestrians.
Personally what I don't like about the narrow streets in Japan is the absence of greenery. In more upmarket neighbourhoods of central Tokyo like Ginza, Marunouchi or Nihombashi there are a few trees on the wide pavements, but still not very green. Here tree line streets are the default. Unfortunately, as Japanese backstreets are so narrow, there is little room for improvement in that regard. But major avenues could benefit from having more trees.