Ogō Yoshitoshi served as a bushō during the Sengoku period.

Yoshitoshi was a descendant of Washio Yoshihisa, a bushō from Settsu Province who served under Minamoto-no-Yoshitsune during the late Heian period (the latter half of the twelfth century).  Minamoto-no-Yoshitsune was an older half-brother of Minamoto-no-Yoritomo, the first shōgun of the Kamakura period.  The family resided in Settsu for generations thereafter.  The Washio family name was used only by lineal descendants, whereas all branches were known by the Ogō family name.  The Ogō were known to serve as resident officials for the administration of security affairs during the Heian and Kamakura periods, and during the Muromachi period served as mokudai, or personal representatives, of the Akamatsu clan (military governors) and the Uragami clan (deputy military governors) in western Harima.

Yoshitoshi initially served the Kodera clan in central Harima.  Yoshitoshi, along with Kodera Yoshitaka (later known as Kuroda Yoshitaka) and Eda Zenbe-e, provided counsel to Kodera Masamoto, head of the clan, with regard to whether to side with the Oda or the Mōri as the two armies headed toward conflict.  Masamoto decided to side with the Oda according to the input from Yoshitaka, whereupon the Kodera temporarily came under the command of the Oda.  In 1578, however, the clan separated from the Oda and Masamoto holed up in Gochaku Castle.  Neither Yoshitoshi nor Zenbe-e appear on the list of primary members of the Kodera clan who remained in the castle.  Yoshitaka continued his support of the Oda, so it is possible that Yoshitoshi did not comply with Masamoto’s decision to reject the alliance.

Later, Yoshitoshi’s younger brother, Ogō Nobuaki, served under Kuroda Yoshitaka in the Kyūshū heitei, or the Pacification of Kyūshū, and was awarded a fief of 5,000 koku.  Thereafter, Yoshitoshi went to Nakatsu in Bizen Province, receiving a fief of 1,370 koku in service of the Kuroda clan.