After the Jokyu Disturbance (1221), the Kikkawa Clan were given the Oasa
area in Geihoku. In 1313, they built Surugamaru Castle at the foot of Kanbiki
Mountain and settled there.
 During the period of Nanbokucho (14th century), their prosperity continued,
and toward the end of the period the clan built Ogurayama Castle in Oasa
Shinjo. Later they became more powerful by serving meritoriously in the Onin
War (1467) and also by developing their successful steel producing business.
They subsequently built Tatsuyama Hachiman Shrine (the tutelary shrine),
Saizenji Temple and Tosenji Temple (both family temples) in the vicinity of
Ogurayama Castle.
 In the middle of the 16th century, the Ouchi Clan and their followers, the Mori
Clan, became influential in the area. The second son of Motonari Mori,
Motoharu, was adopted into the Kikkawa Clan, and he built the spacious
Hinoyama Castle on a hilly site and moved there. The castle was the base from
which the Mori Clan governed. In the vicinity of the castle, Motoharu extensively
built samurai residences and markets as well as his estate, Mantokuin Temple and
Josenji Temple (both family temples).
 In northwestern Hiroshima Prefecture, medieval towns and villages, including
markets and farming fields, castle remains, estates, family temples and tutelary
shrines, have been left relatively untouched.