Gakuganji Masakata served as a bushō during the Sengoku period. He was a retainer of the Mochizuki clan based in the Saku District of Shinano Province. He also had the name of Sōei.
Masakata was a kokujin, or provincial landowner, in Shinano and servant of the Mochizuki clan.
On 2/14 of Tenbun 17 (1548), at the Battle of Uedahara between the Kai-Takeda clan and Murakami Yoshikiyo from the Chiisagata District of Shinano, Masakata served in the vanguard forces on behalf of the Murakami.
During an assault by the Takeda army against Toishi Castle in the ninth month of 1550, Masakata was among the retainers of the Mochizuki holed-up in the castle. This event, which ended in a defeat for the Takeda, is known as the Collapse at Toishi.
According to one source, in 1554, owing to suspicions of collusion with the Nagao clan (Uesugi) of Echigo Province, he was punished by Yamagata Masakage, but this has been noted as an error. Thereafter, he affiliated with the Takeda clan. The name of Sōei Gakuganji appears on a sign dated 3/7 of Kōji 4 (1558) for the reconstruction of the Shakuson Temple by Mochizuki Nobumasa. This type of sign is customarily staked to a building’s ridgepole at construction time stating the building’s donor, builder, date, and reason for construction.
On 8/7 of Eiroku 10 (1567), a written pledge of loyalty from the Shimonogō township to the Takeda clan was donated to the Ikushima-Tarushima Shrine. Masakata submitted a written pledge to Tsuchiya Masatsugu, a hereditary chief retainer of the Takeda.