Having spent the last few days navigating the Tokyo subway system and since most of the Japanese I have met have expressed surprise at this (I’m not sure they use it themselves), I can only say:  it can be done, packed in the morning like sardines, occasionally taking a train in the wrong direction, confusing the JR suburban railway system with the subway system, and sometimes buying the wrong ticket or two.   I can only say that the officials are exceptionally helpful, although few speak English, never more so than on a previous trip when they stopped the escalator for a wheelchair, converted the escalator into a travelling wheelchair platform, and stood to salute top and bottom.   They don’t do that in London.