What geographic factors help explain these variable levels of  urbanization among East Asian cities?

What geographic factors help explain these variable levels of  urbanization among East Asian cities?

East  Asia is a realm of great cities, including many of the largest in the  world. Names like Tokyo, Beijing, and Shanghai represent the mega city  phenomenon like few others.  Upon closer examination, however, one  notices that the countries of this realm display a range of urbanization  levels from very high (Japan and South Korea) to very low (China, for  all its burgeoning cities, remains the least developed in the realm).  What geographic factors help explain these variable levels of  urbanization among East Asian cities? Why does China have more cities in  the one million plus population category than any other country in the  realm and yet the lowest percentage of urbanization? Do you expect the  urban geography of this realm to change, and if so, when and how?