However, this decision was opposed by a faction of the clan led by Kunohe Masazane, a noted warrior who felt that his blood ties to the succession were stronger.

[1] In 1590, during the Siege of Odawara Nobunao led a force of 1000 men, primarily from Sannohe and Hachinohe, and pledged fealty to Toyotomi Hideyoshi.

In return, he was confirmed as daimyō of his existing holdings in northern Mutsu province (the districts of Nukanobu, Hei, Kazuno, Kuji, Iwate, Shiwa and Tōno).

Hideoyoshi subsequently sent a huge army to quell the Kunohe Rebellion which secured Nobunao in his position.

Although his territory was vast geographically, it had an assessed kokudaka of only 100,000 koku, as much of the area was not suitable for growing rice.