Kaifu Tomomitsu served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Miyoshi clan and served as the lord of Kaifu Castle in Awa Province in Shikoku.
According to historical sources from the town of Kaifu, he was a descendant of Prince Washizumi from the Imperial Court in Yamato who had been sent to Sanuki in the era of Emperor Richū during the Kofun period. In the Muromachi period, the Kaifu were based at Yoshino Castle and served the Hosokawa clan who were the military governors of Awa while establishing marital ties with the Miyoshi clan.
Tomomitsu was born as the son of Kaifu Yukichika. There is a theory that Kaifu Castle was constructed by Tomomitsu during the Eiroku era (1558 to 1570).
In 1571, he killed Shima Chikamasu, a younger half-brother of Chōsokabe Motochika (the sengoku daimyō of Tosa Province), who became stranded in Nasa Bay while en route to the Arima hot springs in Harima to convalesce. Upset at the killing of his brother, in 1575 and, again in 1577, Motochika attacked and toppled Kaifu Castle. Thereafter, Tomomitsu purportedly relied upon relatives from Kii Province to safely flee but the details are unknown.