Hira-jiro castles were based on the following two types of buildings: Hokei-yakata buildings, which were samurai residences built in the early Kamakura period and the period of the Northern and Southern Courts (Japan) on flat land surrounded by mounds and walls; and Ta-te buildings, such as the Shugosho (provincial administration offices) where shugo (military governors) lived in the later days of the Muromachi period and the Sengoku period.
平城は、平地に土塁と堀で囲った鎌倉時代初期から南北朝時代(日本)にかけての武士の住まいである「方形館（ほうけいやかた）」、後の室町・戦国時代にかけての守護の居館である守護所などの「館・舘（たて）」がもととなった。