Amakusa is a city located in Kumamoto Prefecture, Japan. As of 31 August 2024, the city had an estimated population of 72,243 in 3602…Amakusa is a city located in Kumamoto Prefecture, Japan. As of 31 August 2024, the city had an estimated population of 72,243 in 36029 households, and a population density of 110 persons per km². The total area of the city is 683.82 km².