I've looked at pictures of Osaka, Tokyo, Nagasaki, Sapporo and there's no sight of any fully traditional urban spaces. Kyoto seems to have a rather small one, but that's it. I understand that Japan suffered a LOT of bombings during WW2 (especially Hiroshima and Nagasaki), but so did many European cities, but they've either rebuilt the historic places or restored them. Why didn't Japan do the same?
I don't understand what you mean by fully traditional urban spaces. Japan is swamped with historical sites both original and restored in urban and rural areas.