The Ogasawara clan itself was also frequently rent by internal political divisions, and proved unable to resist the advance of Takeda Shingen into the province at the start of the Sengoku period.

The Ogasawara took advantage of the confused state of affairs after Nobunaga's assassination to return to Shinano with the support of Tokugawa Ieyasu.

However, Toyotomi Hideyoshi ordered the Tokugawa clan to relocate to the Kantō region in 1590, and the Ogasawara were forced to accompany him, abandoning their castles in Shinano.

[2][3][4] The southern ridge was approximately 500 meters away, and contained the smaller fortification, named the "Hayashi Small Castle", which was the main defensive center.

[5][6][7] The Hayashi large castle was a flat area at the top of the mountain, approximately 100 square meters, surrounded by clay stone walls.