Baba Masafusa served as a bushō during the Sengoku period. Masafusa was a retainer of the Takeda clan of Kai Province. His common name was Baba Minbu-shōyū.
The Baba clan served the Takeda for successive generations. Masafusa was the eldest son of Baba Nobuharu, a clan elder of the Takeda. According to the genealogy of the Yagisawa-Baba clan, Masafusa was born either in 1538 or 1543. On 5/21 of 1575, Nobuharu died while serving as the rear guard to enable the retreat of Takeda Katsuyori in a loss against the Oda army at the Battle of Nagashino. Masafusa then succeeded Nobuharu as the head of the Baba family. Masafusa served as the chamberlain of Makinoshima Castle in Shinano Province. On 9/6 of 1576, Masafusa issued written military regulations to his servants. Around 1577, Masafusa’s servants made offerings to the sacred horse at the Great Shrine of Fujisan-Hongū-Sengen because Masafusa is presumed to have been ill at the time.
According to an authoritative account of Oda Nobunaga known as the Shinchō-kōki, in the second month of 1582, during the Conquest of Kōshū by the Oda clan, Masafusa defended Fukashi Castle in Shinano, but then turned it over to Oda Nagamasu. At this time, he was known as Mino-no-kami, but this was also a common name of Nobuharu. Thereafter, Masafusa’s whereabouts are unknown, and he likely either died in battle or was executed. Based on the genealogy of the Yagisawa-Baba clan, in the fourth month of 1582, he was killed at Makinoshima Castle.
His daughter was wed to Aoki Nobuyasu, the son of Aoki Nobutoki of the Mukawa group, a band of bushi in Kai located near the border areas.