After losing to Tokugawa in the Battle of Sekigahara, Mori's lands around Hiroshima were confiscated and he was moved to Hagi. Amazingly, the Mori family continued to rule over Hagi until the Meiji restoration.

The structure of Hagi Castle is interesting in that it is primarily a Flatland castle but Mori also built a a yagura partway up the mountain and another one at the top in what is called the Tsume no maru. The 5 story donjon, yagura and other structures were demolished in 1874 under the Castle Abolition Law. Only the stone walls were spared. The Hagi Castle ruins are a National Historic Site. The castle town is also a National Historic Site and a famous tourism destination.