When the Otate War which was a succession dispute of the Uesugi clan broke out in June 1578, Ujikuni departed for the front of Echigo together with Ujiteru to assist Kagetora UESUGI as a representative of his older brother Ujimasa who responded to the requirement of reinforcement by a younger brother Kagetora.
天正6年（1578年）5月、上杉氏の家督争いである御館の乱が起こると弟上杉景虎の援軍要請に応じた兄氏政の名代として、氏照とともに景虎支援のために越後に出陣。