 Kunohe Castle was held by Kunohe Masazane (1536–1591), from a branch line of the Nanbu clan who had ruled the region since the early Muromachi period.After the death of the 24th hereditary chieftain of the main Nanbu clan, Nanbu Harumasa in 1582, the clan split into several competing factions.In 1590, the Sannohe faction led by Nanbu Nobunao organized a coalition of most of the Nambu clans and pledged allegiance to Toyotomi Hideyoshi at the Siege of Odawara.