(This is mildly unfair to SF, which actually has a higher population density than Minato-ku, principally because Minato-ku is not a residential neighborhood. But if SF was serious about affordable housing, it would look like Minato-ku rather than "miles of two-story buildings.")
San Francisco Marina which can't build out because of the Pacific. https://www.flickr.com/photos/telstar/15230469/
Tokyo Minato-ku (the "Harbor District") which can't build out because of the Pacific. http://www.realestate-tokyo.com/media/249559/Windows-Live-Wr...
(This is mildly unfair to SF, which actually has a higher population density than Minato-ku, principally because Minato-ku is not a residential neighborhood. But if SF was serious about affordable housing, it would look like Minato-ku rather than "miles of two-story buildings.")