Ujisato, known in his childhood as Tsuruchiyo, was born in Hino, in the Gamō district of Ōmi Province in 1556. In 1568, Oda Nobunaga, who was en route to Kyoto, defeated the Rokkaku clan, who were the masters of Tsuruchiyo's father, Katahide. Upon the Rokkaku clan's defeat, Katahide as a former influential vassal, pledged loyalty to Nobunaga, and became an Oda retainer. However, the price of Katahide's pledge was giving up his son as a hostage, and so Tsuruchiyo was taken to Gifu, then the Oda clan's headquarters. Tsuruchiyo's sagacity impressed Nobunaga, and soon, the young man had his manhood rite in Gifu, taking the name Utahide. In the summer of 1569, Utahide took part in his first campaign, during Nobunaga's subjugation of Kitabatake Tomomasa of Kizukuri Castle. For his distinction in battle, Nobunaga gave his daughter Fuyuhime in marriage to Utahide, affectionately referring to Utahide as "my little son-in-law." At the same time, he was allowed to return to his father's castle at Hino. Though Fuyuhime was still young at this point, she is said to have later matured into a stunningly beautiful woman. .
In 1570, Utahide fought at the Battle of Anegawa, and later that same year, joined his father in the Oda assault on the Asakura clan of Echizen Province. The two led a force of 1,000 men as the vanguard of Shibata Katsuie's army. The total number of men under Katsuie's overall command at that battle totaled 5,000. Of those 5,000, the number under Katsuie's command totaled 600, so this may give some impression of the importance of the Gamō family. Following the betrayal of Azai Nagamasa, Utahide assisted in Nobunaga's withdrawal by taking him into his own Hino Castle, and facilitating his escape to Gifu from there. In recognition of this feat, Nobunaga gave Utahide and his father a stipend increase, and posted them to southern Omi, under the command of Shibata Katsuie. The Gamō would see action against the Asakura once more, in 1573. In 1575, upon Katsuie's posting to Kitanoshō Castle, the Gamō, ruling from their castle at Hino, came under Nobunaga's direct command, serving as hatamoto. In 1581, he participated on Second Tenshō Iga War in the Siege of Hijiyama.
In 1588, construction was completed on Matsusaka Castle, where he immediately moved. Ujisato took part in all of Hideyoshi's subsequent campaigns: Kyushu Campaign, the Siege of Odawara, the pacification of Ōshū , and the Japanese invasions of Korea. For his role in the pacification of Ōshū, he received a 420,000 koku fief with its headquarters at Kurokawa Castle in Aizu. He renamed the castle Wakamatsu, the name which even the town retains to this day. In preparation for the Japanese invasions of Korea, Ujisato proceeded in 1592 to Hideyoshi's base in Nagoya in Hizen Province. He fell ill there, coughing up blood in early 1593. From Nagoya, he headed first to Aizu, and then to Fushimi, where the Gamō family's mansion was almost complete. Hideyoshi himself would visit the mansion twice after its completion Ujisato died at age 40, at Fushimi Castle. Though his family would lose Aizu soon after with Hideyuki's transfer to Utsunomiya, the Gamō would later be returned to Aizu by Tokugawa Ieyasu.
