Onamihime was married off to Nikaidō Moriyoshi and they had two sons, Heishiro and Yukichika. Heishiro was sent off as a hostage with the powerful Ashina clan and was adopted turning Ashina Moritaka. After Moriyoshi and Yukichika death, Onamihime became the owner of the Sukagawa castle, chief representative of the Nikaido clan and took nun name of Daijou-in. Due to the death of Date Masamune's father, Date Terumune by the hands of Nihonmatsu Yoshitsugu, Masamune swore vengeance, launching an attack against the Nihonmatsu in 1585. She fought in the Battle of Hitotoribashi alongside Ashina, Sōma, Hatakeyama and Satake against Date clan. The allies marched with their 30,000 troops toward Motomiya Castle. Masamune with only 7,000 troops prepared a defensive strategy, Onamihime commanded her troops to attack but Masamune used a strategic defense and the allied forces retreated. In 1588, Onamihime allied again with Ashina and Sōma clan to counter Date Masamune in Battle of Koriyama. The Battle of Suriagehara started in July 1589, Date masamune defeated Ashina and Satake troops and was given the victory of Date army, consolidating of power in Southern Mutsu. After this Date Masamune asked his aunt to come surrender, but she strongly refused. Onamihime and Ishikawa clan continued with resistance. She defended herself against the attack at the castle, when her vassal Hodohara Yukifuji betrayed the Nikaidō clan to the Date and helped Masamune take Sukagawa Castle, in October 26 1589, the castle fell. Masamune saved his aunt Onamihime life, and had her escorted safely to live in retirement at Suginome Castle. However, she wasn't going to live with this, Onamihime who hated Masamune left to live with Iwaki Tsunetaka, who was another nephew. After his death, she went to Satake Yoshinobu. The Satake clan allied to the Western Army and Onamihime went along in the Battle of Sekigahara. Following the defeat of the Western Army by the Tokugawa Ieyasu Eastern Forces, the Satake Clan was allowed to continue existing, but was punished. The Satake's was moved to Dewa by Tokugawa order in 1602, and it was on the way up to Dewa, while passing her old castle in Sukagawa, that Onamihime died in 1602 and was buried there.
