Upon assuming control, the Asano clan enjoyed a favorable relationship with the Tokugawa clan, which granted them the freedom to establish a new castle. At the time, the region resembled a coastal island, with only a small mansion of the Ikeda family remaining. The Asano clan embarked on extensive land reclamation and expansion efforts, culminating in the completion of Akō Castle in 1661. This achievement not only transformed the landscape but also solidified their legacy.