Yatsushiro is an old castle town (Yatsushiro-jô) and served as a secondary residence of the HOSOKAWA clan during the Edo period (1603-1868). The city is located in the southern part of central Kumamoto Prefecture – south of Kumamoto and north of Kagoshima – and has the second-largest population (116,000 as of 2026) in the prefecture. The sediment carried by the Kuma River, which flows through the center of the city, together with the large tidal differences of the Shiranui Sea, made land reclamation possible. Since the Edo period, approximately 4,000 hectares of new land have been reclaimed.