Nishio City is located at the southern end of the Yahagi River basin in Aichi Prefecture, surrounded by mountains such as Mt. Yatsumen and Mt. Hakaku. The town has a long history, and thanks to its fertile soil and warm climate, people have lived here since the Jomon period. Built during the Kamakura period, Saijo Castle served as the base of the region, and it flourished as the castle town of the Okuyu Matsudaira clan, with a fiefdom of 60,000 koku. Today, as a core city in the southern part of West Mikawa, the city continues to develop, centered around the automobile-related industry. Nishio boasts one of Japan's leading producers of matcha, also known as tencha, and is also a growing production base for agricultural and marine products such as carnations, farmed eels, and clams. The entire city area is designated as Mikawa Bay Quasi-National Park, a popular scenic spot.