Gunji Toshiyoshi served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a senior retainer of the Tamura clan of Mutsu Province.
In 1586, Kiyoaki suddenly died, marking a series of deaths of the head of the clan (Moriaki → Yoshiaki → Takaaki → Kiyoaki). Kiyoaki did not have an heir. In his will, he stated that if Masamune and Megohime have a child, then have the child become his adopted successor. Nevertheless, Kiyoaki’s widow (the daughter of Sōma Akitane) sought to have a member of the Sōma family become the successor. This resulted in a succession struggle known as the Tenshō Tamura Disturbance.
Toshiyoshi, together with a clan elder and family member named Tamura Akimori, joined the faction of Sōma Yoshitane in opposition to Tamura Akiyori on the side of Date Masamune. In 1589, during an attack by the Date army, Toshiyoshi died in battle at Shizue Castle.