The Chūgoku region, also known as the San'in-San'yō region, is the westernmost region of Honshū, the largest island of Japan. It consists of the prefectures of Hiroshima, Okayama, Shimane, Tottori and Yamaguchi.
In Prince of Tennis[]
The mentioned only school, Hikogashima, hails from this region, more specifically the Yamaguchi Prefecture.