Mishuku Tomotsuna served as a bushō from the Sengoku to early Edo periods.  He also served as a physician for Takeda Shingen, the sengoku daimyō of Kai Province.

In 1546, Tomotsuna was born as the son of Katsurayama Harima-no-kami Tsunaharu and the grandson of Katsurayama Sadauji.  His mother was the younger sister of Atobe Yasutada, a hereditary retainer of the Kai-Takeda clan.

Tomotsuna was a member of the Katsurayama clan, influential kokujin, or provincial landowners, in the Suntō District of eastern Suruga Province.  Tomotsuna was a nephew of Katsurayama Ujimoto, a senior retainer of Imagawa Yoshimoto.

From an early age, Tomotsuna served Takeda Shingen.  Owing to his relationship to the Katsurayama clan, Tomotsuna served as a proxy (guardian) in battle for Katsurayama Nobusada, the sixth son of Takeda Shingen adopted by Katsurayama Ujimoto.  When Shingen was ill in his latter years, Tomotsuna joined Itasaka Sōshō as a physician to treat Shingen.  In the twelfth month of 1580, Tomotsuna transferred the headship of the clan to his eldest son, Mishuku Masatomo and retired.  There is a story that Masatomo was not the natural son of Tomotsuna but, instead, the son of Katsurayama Nobusada.

In the third month of 1582, the Kai-Takeda clan were decimated by Oda Nobunaga in the Conquest of Kōshū (Kai).  Thereafter, Tomotsuna served the Gohōjō clan.  In 1590, after the fall of the Gohōjō to the Toyotomi in the Conquest of Odawara, Tomotsuna served the Tokugawa clan.

He died on 3/21 of Keichō 11 (1606).  He was sixty-one years old.