Kaminoyama Yoshifusa served as a bushō during the Sengoku period. He was the lord of Kaminoyama Castle in Dewa Province.
The Kaminoyama were a branch of the Tendō clan who were members of the Satomi family. With respect to lineage, the clan began after the assignment to Kaminoyama of Tendō Mitsunaga, the son of Tendō Yorinao who was the grandson of Shiba Kaneyori, the founder of the Mogami clan from the early fourteenth century.
During the Eishō era (1504 to 1521), the Date army repeatedly invaded the territory of Kaminoyama. In 1508, Yoshifusa’s base at Takadate Castle was toppled whereupon Yoshifusa fled with a small group of retainers and took refuge in Tendō Castle. Koyanagawa Masanori of the Date family entered Takadate Castle. After Date Tanemune invaded the Murayama district in the second month of 1514, the Date fought against the Mogami, the Tendō, the Yamanobe, the Sagae, and other local clans at Hasedō. Mogami Yoshisada, a sengoku daimyō, was defeated and, in the twelfth month, settling with the Date on the condition that he wed the younger sister of Tanemune, thereby placing the Mogami under the command of the Date.
In 1520, Yoshisada died without a designated heir. The Date clan then devised a plan to send a child for adoption by the Mogami to make the Mogami serve as their puppets. The kokujin from the Murayama district, however, gradually began to resist the Date. Noticing this development, Yoshifusa suddenly appeared and launched another rebellion joined by Sagae Takahiro (the lord of Sagae Castle) and Tendō Yorinaga (the lord of Tendō Castle), the Narusawa clan and other influential kokujin. This led Date Tanemune to attack Kaminoyama with great force and Yoshifusa was killed in battle.
Tanemune proceeded to capture Yamagata, Tendō, and Takadama. The following year, he attacked the Sagae clan and compelled a settlement by which the Sagae came under his command. As a result, the Mogami as well as kokujin located in the Murayama district, came under the control of the Date clan, but a rebellion by Yoshifusa and others also tested the Date. Aware of the power of the kokujin, Tanemune discarded a plan to send a child to the Mogami for adoption, and, instead, allowed Mogami Yoshimori of the Nakano clan (who were members of the Mogami) to succeed to the headship of the clan.
In 1535, Yoshifusa’s son, Buei Yoshitada, recaptured Takadate Castle and constructed Kaminoyama Castle (Tsukioka Castle). The era of Yoshitada’s grandson, Kaminoyama Mitsukane, witnessed an event known as the Tenshō Mogami Conflict and he came into conflict with Mogami Yoshiaki. After the end of the conflict, in 1580, Mitsukane was killed by retainers, Satomi Yoshichika and Satomi Minbu (father and son), who colluded with Yoshiaki, marking the end of the bloodline of the Kaminoyama clan.