The Yatsushiro Shinchi district of Sencho-machi is reclaimed land built in 1855 in collaboration by the Hosokawa clan (whose mansion was in Ninomaru, Kumamoto Castle) and the Yatsushiro Castle Lord Matsui clan. The "Ozaya-bushi", which was born from the reclamation work of the "Yonhyaku-cho Shinchi", has been handed down as the Shinchi Ozaya-bushi. "Ozaya" derives its name from a magnificent doubled stone wall built to strengthen the locks (a facility for allowing drainage and preventing backflow of seawater) built at the time of land reclamation. Designated as a Kumamoto Prefecture historic site, the series of locks abuts the Shinchi district, and a monument as the "Birthplace of Oyasabushi" has been built.