[1][2] Kagomori Castle is located on a hill bordered by the Hiromi-gawa river in the center of the town of Matsuno, in the southern Ehime prefecture.

It is unknown when this strategic chokepoint was first fortified, but it appears to have been in the 14th century by the local Watanabe clan, on the main retainers of the Saionji family who dominated southwestern Iyo Province.

[3][4] The Saionji were court nobility from Kyoto and maintained close relations with the Tosa-Ichijō clan who held the estate of Nakamura on the opposite side of the border.

However, the very next year, Toyotomi Hideyoshi launched an invasion of Shikoku and quickly forced the Chōsokabe back to Tosa Province.

When ordered to send troops to the invasion of Korea in 1592, he cut down large trees in shrines and temples throughout his domain to construct ships.

As was common for the time, it consisted of ten enclosures spread along the ridge of the hill, separated by clay walls and dry moats.