Kumamoto is the capital city of Kumamoto Prefecture on the island of Kyushu, Japan.As of March 1, 2010, the city has an estimated population of 731,286 and a population density of 1,880 persons per km². The total area is 389.53 km².Greater Kumamoto had a population of 1,460,000, as of the 2000 census. It is not considered part of the Fukuoka–Kitakyushu metropolitan area, despite their shared border. The city was designated on April 1, 2012 by government ordinance.