Nishio is a city located in Aichi Prefecture, in the Chūbu region of Japan. As of 1 October 2019, the city had an estimated population of 169,984 in 65,553 households, with a population density of 1,054 persons per km2. The total area of the city was 160.22 square kilometres (61.86 sq mi). It is a regional commercial and manufacturing center and the country's leading producer of powdered green tea.

Aichi Prefecture is a prefecture of Japan located in the Chūbu region of Honshū. Aichi Prefecture has a population of 7,552,873 and a geographic area of 5,172.92 square kilometres (1,997.28 sq mi) with a population density of 1,460 inhabitants per square kilometre (3,800/sq mi). Aichi Prefecture borders Mie Prefecture to the west, Gifu Prefecture and Nagano Prefecture to the north, and Shizuoka Prefecture to the east. Nagoya is the capital and largest city of the prefecture.