Ōsuga Kyūbei-no-jō served as a bushō during the Sengoku period.  He was a dogō, or small-scale landowner, in the Sarashina District of Shinano Province.

The Ōsuga were members of the Chiba clan descended from the Kanmu-Heishi.  Kyūbei-no-jō obeyed Murakami Yoshikiyo, the sengoku daimyō based in the Chiisagata District of Shinano, to resist the Invasion of Shinano led by Takaeda Harunobu (Shingen).  However, he colluded with the Takeda and, in 1553, toppled Koraku Castle, one of the outlying castles constructed on a steep mountain by Yoshikiyo to defend his main base at Katsurao Castle.  In the course of this operation, he killed the commander of the castle, Kojima Hyōgo-no-suke, and caused disarray among the defenders of the Murakami.  Kyūbei-no-jō then entered service for the Takeda family.

Kyūbei-no-jō also served valorously in battles in Fuse.  In 1557, he received a medal of honor from Harunobu for capturing Koraku Castle.  On 9/11 of Kōji 1 (1555), in the northern part of Shinano, when the Takeda forces confronted the forces of Nagao Kagetora (later known as Uesugi Kenshin) of Echigo Province, an incident occurred whereby someone from Asahiyama Castle who colluded with the Nagao clan set fire to a hut.  Kyūbei-no-jō received a commendation from Harunobu for apprehending the person suspected of committing this act.

Thereafter, Kyūbei-no-jō served Takeda Shingen and Takeda Katsuyori, making contributions on the battlefield.  On 5/21 of Tenshō 3 (1575), at the Battle of Nagashino, he was killed in action along with his son, Ōsuga Mokutarō.  The following year, his territory was inherited by his younger brother, Ōsuga Kojirō.