Kyogoku Takahisa in the 14th century, lived in Amako-go (Izumo Province), and took the name 'Amago'.

They were Shugodai (vice-Governors) of Izumo and Oki provinces for generations, for the Kyogoku Shugo branch, and their seat was Gassan Toda castle.

In 1484, Amago Tsunehisa (1458–1541), was deprived of the position of Shugodai by Kyogoku Masatsune, who was the Shugo, because he did not obey the request of tax from the Muromachi bakufu, and was expelled from Gassan Toda castle.

Although Enya Kamonnosuke was dispatched to Gassan Toda castle as the new Shugodai, Tsunehisa recaptured Gassan Toda castle by a surprise attack in 1486, took control of Izumo, and developed the Amago clan into a Sengoku Daimyo clan.

[1] Amago Katsuhisa tried to regain prestige for the clan by joining the forces of Oda Nobunaga, invaded Tajima and Inaba Provinces, but was defeated and died in the siege of Kōzuki by the Mōri in 1578.