Kaminoyama Mitsukane served as a bushō during the Azuchi-Momoyama period. He was the lord of Kaminoyama Castle in Dewa Province.
The Kaminoyama were a branch of the Tendō clan, powerful kokujin, or provincial landowners, in Dewa. For this reason, some members of the clan also adopted the Satomi surname. Mitsukane cooperated with the Tendō clan. From the era of his grandfather, the family adopted the surname of the Buei clan. Mitsukane also adopted the name of Buei Yoshimasa.
Mitsukane was born as the son of Buei Yoshisada.
Mitsukane wed the daughter of Nakano Yoshikiyo (the younger sister of Mogami Yoshimori) and thereby became a relative of the Mogami. He also had contacts with the Tendō clan who comprised the main branch of the family. Furthermore, to stabilize his territory, he endeavored to improve relations with the Date with whom the family had conflicts from the era of his great-grandfather, Kaminoyama Yoshifusa. In an internal dispute that erupted in 1574 known as the Tenshō Mogami Conflict, Mitsukane initially joined forces with Mogami Yoshiaki. After the Date army backing Yoshimori advanced to Tarushita near Kaminoyama, he betrayed Yoshiaki and allowed the Date army to pass-through. As a result, he came into conflict with Mogami Yoshiaki.
In 1578, after the collapse of peace efforts, Mitsukane allied with Date Terumune to attack the Mogami, imposing significant losses. As a member of a branch of the Tendō, Mitsukane served as a key figure in an alliance of kokujin in Dewa known as the Mogami yatsudate, or Eight Shields of the Mogami (also known as the Eight Shields of the Tendō) formed, in part, to resist the influence of the Date clan. In 1577, after battle erupted between the Tendō and Mogami, despite a settlement, Mitsukane was in communication with Tendō and Date forces opposed to Yoshiaki. This caused Yoshiaki to remain vigilant of Mitsukane.
In 1580, Satomi Yoshichika and Satomi Minbu (father and son) who were senior retainers of Mitsukane and family members were lured away by retainers of the Mogami including Ujiie Morimune and Yagashiwa Naoie to collude with Yoshiaki. Minbu murdered his older brother, Satomi Kuranosuke, who was a supporter of Mitsukane. Mitsukane was then attacked by Yoshiaki. Minbu subsequently killed Mitsukane and became the lord of Kaminoyama Castle. The Kaminoyama-Satomi clan continued in name thereafter.
Later, Minbu was suspected of being complicit in the premeditated murder of Mogami Yoshiyasu and was killed. Meanwhile, Satomi Motokatsu, the orphan of Satomi Kuranosuke, killed many members of Minbu’s family to avenge the death of his father and served the Date family.