Yashio is a city located in Saitama Prefecture, Japan. As of 1 January 2021, the city had an estimated population of 92,512 in 44,288 house…Yashio is a city located in Saitama Prefecture, Japan. As of 1 January 2021, the city had an estimated population of 92,512 in 44,288 households and a population density of 5100 persons per km². The total area of the city is 18.02 square kilometres.