Lifespan: Eishō 7 (1510) to 10/21 of Kōji 2 (1556)
Father: Kōsokabe Michinaga
Adoptive Father: Kōsokabe Chikahide
Siblings: Chikahide, Hidemichi
Wife: [Formal] Daughter of Hosokawa Sadasuke
Children: Yasuyoshi, Hidemasa, daughter (formal wife of Kōsokabe Chikayasu)
Kōsokabe Hidemichi served as a bushō during the Sengoku period. He was a kokujin, or provincial landowner, in Tosa Province.
In 1510, Hidemichi was born as the second son of Kōsokabe Michinaga, a kokujin in the southeast portion of the Kami District of Tosa. Kōsokabe Chikahide was his older brother.
After inheriting the headship of the clan, in 1526, Chikahide attacked the Aki clan, landlords in the Aki District of Tosa, but lost his son and designated heir, Kōsokabe Hideyoshi, en route to suffering a major defeat. As a result, he adopted Hidemichi. Later, Chikahide adopted the monk’s name of Sensen and retired.
The Kōsokabe clan, however, began to wane in influence. Seeking a revival and fearing the expansion of power wielded by Chōsokabe Kunichika, Chikahide adopted Kunichika’s third son, Chikayasu, creating a conflict with Hidemichi. Hidemichi was fiercely opposed to joining forces with Kunichika. In the end, on 10/21 of Kōji 2 (1556), Chikahide ordered his retainers to assassinate Hidemichi. He was forty-seven years old.
Chikayasu then became Chikahide’s heir under the name of Kōsokabe Chikayasu, inheriting the headship of the clan. Chikahide continued to support him after retiring. In addition, Chikahide took care of Hidemichi’s eldest son, Yasuyoshi, who adopted the surname of Nakayamada, becoming a chief retainer in the clan.
His grave is in a graveyard alongside the Kami Shrine in the town of Noichi in the city of Kōnan in Kochi Prefecture. Retainers who martyred themselves on behalf of Hidemichi are also buried there. In 1893, a descendant named Takeda Hidenobu built a memorial there inscribed with the name of Kōsokabe Hidemichi. After his death, Hidenobu was also buried in this location.