Kasuga is a city located in Fukuoka Prefecture, Japan. As of 31 March 2024, the city had an estimated population of 111,840 in 50874 hous…Kasuga is a city located in Fukuoka Prefecture, Japan. As of 31 March 2024, the city had an estimated population of 111,840 in 50874 households, and a population density of 260 persons per km². The total area of the city is 14.145 km².