北條氏康
In 1555, Hōjō Ujiyasu ordered an attack on Ōgo castle, now commanded by Kamiizumi. Kamiizumi surrendered the castle without a fight, and joined Ujiyasu. This same year, Uesugi Kenshin invaded western Kōzuke in order to re-take Hirai Castle. Kamiizumi abandoned the Hōjō side, and sent messages to the Uesugi. He became one of Uesugi's generals, and helped the Uesugi drive out the Hōjō forces. Kenshin seized total control of Kōzuke, installed Nagano Narimasa as governor in Minowa Castle, and returned to his base in Echigo.