The housing space metrics seem very far off from my experience, looking at numbers it seems "Tokyo" means "Tokyo Metropolis", which includes the countryside, mountains, etc. So it's not really comparing the city. If we look at the numbers for Tokyo 23 wards[1] (what would traditionally be called "the city"), we can see they are virtually half than those from Paris or London: 16.5-19.7sqm/person is the range that fall…
And indeed, people throughout Greater London are entirely used to living in small, damp, shared boxes.