Lifespan: Eishō 5 (1508) to 12/30 of Tenshō 2 (1575)
Other Names: Yūki Rokurō (?), 命察 (monk’s name)
Rank: bushō, sengoku daimyō
Title: Governor of Shimotsuke
Clan: Yūki → Oyama
Father: Yūki Masatomo
Siblings: Yūki Masanao, Yūki Masakatsu, Takatomo, sister (wife of Utsunomiya Hisatsuna)
Children: Hidetsuna, Tomioka Hidetaka, Yūki Harutomo, daughter (formal wife of Edo Shigemichi)
Oyama Takatomo served as a bushō and sengoku daimyō during the Sengoku and Azuchi-Momoyama periods. Takatomo was the seventeenth head of the Oyama clan, known as an intrepid warrior representing Shimotsuke Province.
In 1508, Takatomo was born as the third son of Yūki Masatomo. He received one of the characters from the name of Ashikaga Takamoto, the Koga kubō, and adopted the name of Takatomo. In 1519, in accordance with the will of Takamoto, an individual named Yūki Rokurō was included among the bushō who attacked the Mariyatsu clan at Shiizu Castle in Kazusa Province (who were allied with Ashikaga Yoshiaki, the Oyumi kubō). This individual is surmised to be in reference to Takatomo. Around 1535, Takatomo became the adopted heir of Oyama Masanaga and inherited the Oyama clan. Moreover, at this time, he ousted another adopted son, Koshirō, who came from the Yamakawa clan.
After becoming the head of the Oyama clan, he aimed to unify his band of retainers by relying upon force to compel rebellious retainers to abide by him, while promising rewards such as land to cooperative retainers. He also sought to resolve both internal and external problems, engaging in peace negotiations with surrounding landlords for a cessation of hostilities and the recovery of territory earlier lost. Owing to these achievements, the Oyama family restored its power and attained a state of relative stability.
Takatomo also cooperated with his father, Masatomo, and his older brother, Yūki Masakatsu, fighting against opponents of the Yūki clan. In 1547, after the death of Masatomo, the Utsunomiya clan of Shimotsuke used the opportunity to attack the Yūki, but Takatomo combined forces with his brother to repel them. In 1549, Hōjō Ujiyasu launched a plot to back Ashikaga Yoshiuji as the successor to Ashikaga Haruuji (the Koga kubō and lineal heir of Ashikaga Takamoto). Yoshiuji was Haruuji’s second son. Meanwhile, Takatomo opposed him by backing Ashikaga Fujiuji, the eldest son and lineal heir of Haruuji. Takatomo’s older brother, Masakatsu, succombed to the pressure and joined the faction backing Yoshiuji, while Takatomo’s eldest son and lineal heir, Oyama Hidetsuna, also backed Yoshiuji. As a result, Takatomo was forced into retirement and, around 1560, transferred headship of the clan to Hidetsuna. After the death of his older brother, Masakatsu, Oda Ujiharu used this opportunity to assault Yūki Castle, but, upon this occasion, Takatomo was staying in the castle and led forces from the Oyama and Yūki armies to repel Ujiharu.
In 1561, during the Siege of Odawara Castle, Takatomo aligned with Uesugi Kenshin, serving as a member of the Uesugi army. At the ceremony to appoint Kenshin as the deputy shōgun of the Kantō, he was dissatisfied about an incident in which Chiba Tanetomi claimed the head seat among the daimyō from the Kantō attending the event. Soon thereafter, Takatomo joined forces with Hōjō Ujiyasu, angering Kenshin. In 1562, Takatomo was attacked by Kenshin and surrendered. Later, he transferred Oyama Castle to Hidetsuna and retreated to Enomoto Castle in the Tsuga District of Shimotsuke. Around 1570, he entered the priesthood and adopted the monk’s name of 命察.
In 1575, after preparing for an attack against Hōjō Ujimasa, he suddenly died.
In 1559, after the death of his older brother, Yūki Masakatsu, Takatomo’s third son, Yūki Harutomo, succeeded to the headship of the Yūki clan. In his latter years, Takatomo sent a letter to the abbot of the family temple of the Yūki and said: “Around the time that I inherited the Oyama clan, I was concerned that if something occurs that my parents (Yūki Masatomo and his wife) would come to Oyama, but, thinking of Harutomo, I really understand the feelings of my parents.” He then requested, in lieu of himself, for support for Harutomo. Meanwhile, around the same time, Harutomo sent a letter to the abbot noting that he heard his father was of ill health, and that he was distressed over the sin of attacking his father even though it was to protect the Yūki clan in turbulent times.
Around this time, the Kantō area was significantly impacted by internal conflicts in the family of the Koga kubō along with disputes between the Gohōjō and Uesugi clans. There were many instances of clashes between father and son, or between other members of the same family, and the Oyama and Yūki clans appeared to be no exception to these troubles.