Minowa Castle's lord Nagano Narimasa reportedly repelled Takeda Shingen's attacks six times, earning fame as an impregnable fortress — Shingen is said to have lamented that Kozuke could never be conquered while Narimasa lived. After Narimasa's death, the castle fell to the Takeda around 1563, and Naito Masatoyo became its lord governing western Kozuke.

Nagano Narimasa, who built Minowa Castle in 1512, defended it as the key stronghold of western Kozuke Province while serving the Uesugi clan as Kanto Kanrei. Through skillful tactics, he repelled Takeda Shingen's invasions six times over his lifetime, reportedly leading Shingen to lament, "As long as Narimasa alone stands, Kozuke cannot fall." When Narimasa died of illness in 1561, the castle lost its unifying leader and soon fell to the Takeda.