Tosa is a city located in Kōchi Prefecture, Japan. As of 1 August 2022, the city had an estimated population of 26,427 in 12,671 households an…Tosa is a city located in Kōchi Prefecture, Japan. As of 1 August 2022, the city had an estimated population of 26,427 in 12,671 households and a population density of 290 persons per km². The total area of the city is 91.50 square kilometres. The city of Tosa should not be confused with the historical Tosa Province, which covered all of modern-day Kōchi Prefecture.