Asaka is a city located in Saitama Prefecture, Japan. As of 1 January 2021, the city had an estimated population of 143,195 and a populati…Asaka is a city located in Saitama Prefecture, Japan. As of 1 January 2021, the city had an estimated population of 143,195 and a population density of 7800 persons per km². The total area of the city is 18.34 square kilometres.