Mitoyo is a city located in Kagawa Prefecture, Japan. As of 31 September 2022, the city had an estimated population of 59,876 in 23024 houseā¦Mitoyo is a city located in Kagawa Prefecture, Japan. As of 31 September 2022, the city had an estimated population of 59,876 in 23024 households and a population density of 270 persons per km. The total area of the city is 222.73 square kilometres.