Lifespan: Tenbun 6 (1537) to 8/29 of Bunroku 2 (1593)
Rank: bushō, daimyō
Title: Junior Fifth Rank (Lower), Governor of Tōtōmi
Lord: Saitō Tatsuoki → Toyotomi Hideyoshi
Father: Katō Kageyasu
Siblings: Mitsuyasu, Mitsumasa
Wife: [Formal] Daughter of Hitotsuyanagi Kayū
Children: Sadayasu, daughter (formal wife of Takenaka Shigekado), Mitsunao, Mitsuyoshi
Katō Mitsuyasu served as a bushō and daimyō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of Toyotomi Hideyoshi. He had the common names of Sakunai and Gonbei.
In 1537, Mitsuyasu was born as the eldest son of Katō Kageyasu in Hashizume in the village of Imaizumi in the Tagi District of Mino Province. Initially, he was known as a brave warrior serving Saitō Tatsuoki, but after the fall of Inabayama Castle that left the Saitō clan as nomads, he became a rōnin, or wandering samurai, and fled to Ōmi Province. During battle against the forces from Mino, Oda Nobunaga noticed the valor of Mitsuyasu so, through the mediation of Kinoshita Hideyoshi (later known as Toyotomi Hideyoshi), Mitsuyasu was permitted to meet with Nobunaga, whereupon he was engaged to serve as a retainer of Hideyoshi.
In 1571, when Azai Nagamasa attacked the Yokoyama fortress, Mitsuyasu successfully repelled him. Hideyoshi then granted him a fief of 700 kan in the village of Isono in the Sakata District of Ōmi along with ten yoriki, or security officers, under his command.
In 1578, after the assault on Miki Castle in Harima Province, he was further awarded 5,000 koku in Harima. In 1582, at the Battle of Yamazaki, Mitsuyasu joined Ikeda Tsuneoki and others to cross the Enmyōji River to launch a surprise attack against Tsuda Nobuharu. Taking advantage of the chaos on the part of the enemy forces, he attacked the main division of Akechi Mitsuhide, causing them to flee in disarray while leading Hideyoshi’s army to victory. Owing to these contributions, he was granted a fief of 15,000 koku around Shūzan Castle in Tanba Province – triple the size of his landholdings in Harima. Thereafter, Mitsuyasu was transferred to Kaizu Castle in Ōmi and his fief increased to 20,000 koku. Next, he moved to Takashima Castle (Ōmizo Castle) in Ōmi and then Inuyama Castle in Owari Province.
In 1583, at the Battle of Shizugatake, he served as a military magistrate for Shibata Katsuie. In 1584, after defending Inuyama Castle during the Battle of Komaki-Nagakute, he served valorously in the battle to pursue Sassa Narimasa. In 1585, Mitsuyasu became the lord of Ōgaki Castle in Mino and his fief was increased to 40,000 koku. At the same time, he was assigned responsibility to manage 20,000 koku of landholdings under the direct jurisdiction of the Toyotomi. Mitsuyasu, however, treated this as his own income-producing land, inviting scorn from Hideyoshi. In the ninth month of the same year, his landholdings were confiscated and he was turned over to Toyotomi Hidenaga and lived in confinement in Kōriyama Castle in Yamato Province.
In 1587, Mitsuyasu was pardoned and received a fief of 20,000 koku around Sawayama Castle. He was then conferred the titles of Junior Fifth Rank (Lower) and Governor of Tōtōmi. Thereafter, he was frequently called enshū-taishu, or Governor-General of Tōtōmi. In 1590, during the Conquest of Odawara, Mitsuyasu guarded Sunpu. Together with other bushō, he captured Yamanaka Castle. During that battle, Hitotsuyanagi Naosue, the lord of Ōgaki Castle, was killed in action so, accompanying the transfer of Hashiba Hidekatsu to Gifu in Mino Province, Mitsuyasu received further recognition with a fief of 240,000 koku in Kai Province.
Kai was on the border of the eight provinces in the Kantō controlled by Tokugawa Ieyasu. After entering the province, Mitsuyasu assigned the governing duties for Kai and Kawachi provinces to his eldest son and designated heir, Katō Sadayasu, and Mitsuyasu’s younger brother, Mitsumasa. He further assigned the Gunnai region to his adopted son, Katō Mitsuyoshi. Until 1592, Mitsuyasu managed on a centralized basis the security of and donations to shrines and temples, the issuance of tax exemptions, and so on, in addition to land surveys. The surveys conducted at this time served as the basis for Hideyoshi to determine the service requirements for local lords and collections. Mitsuyasu also commenced the construction of Kōfu Castle.
Beginning in 1592, for the Bunroku Campaign on the Korean Peninsula, Mitsuyasu requested to join and, while away on his deployment, he maintained close contact with Mitsuyoshi who remained behind, providing advice on governance of the territory. In the ninth month of 1593, he planned to return to Japan but fell ill while encamped at Seosaengpo and died at the age of fifty-seven.
His remains were returned to Japan and interred at the Kai-Zenkō Temple in the village of Itagaki in the Yamanashi District of Kai. His grave was later transferred to the Sōkei Temple in Ōzu in Iyo Province.
Theory regarding poisoning
After the death of Mitsuyasu, the youth of his son, Sadayasu (Sakujūrō), was used as justification for his territory to be forfeited. In the first month of 1594, Sadayasu transferred to Kurono in Mino Province. After a period without a provincial lord, the governance of Kai was awarded to Asano Nagamasa and his son, Asano Yukinaga.
According to one source, while serving in the Bunroku Campaign, Mitsuyasu came into conflict with Ishida MItsunari. Mitsunari invited him for a meal at the base of Miyabe Nagafusa, after which Mitsuyasu fell ill. He drew-up a will and soon died, stating that he was poisoned by Mitsunari. There is research recognizing the validity of this theory. At a minimum, it is believed that the theory of poisoning existed in the same era, and it was deemed unjustly suspicious that magistrates refused to recognize the inheritance by Sadayasu of his father’s landholdings. During the Toyotomi administration, however, in the event of an inheritance by successors who were in their youth, there were many cases whereby the fief was reduced owing to challenges with respect to management of the territory and cases whereby the successors were transferred away from strategic locations.
At the Battle of Sekigahara during which Mitsunari sought to overthrow Ieyasu, Sadayasu affiliated with the Eastern Army led by Ieyasu in opposition to the Western army led by Mitsunari. After this battle, Sadayasu received recognition of his rights to his landholdings and later became the first lord of the Ōzu domain in Iyo Province.