Lifespan: Tenbun 1 (1532) to 3/18 of Eiroku 4 (1561)
Titles: Lieutenant of Outer Palace Guards of the Left Division, Chief of the Left Division of Outer Palace Guards, Senior Assistant Minister of Popular Affairs, Governor of Sanuki
Lord: Miyoshi Nagayoshi
Father: Miyoshi Motonaga
Adoptive Father: Sogō Kageshige
Siblings: Miyoshi Nagayoshi, Miyoshi Jikkyū, Atagi Fuyuyasu, Kazumasa, Noguchi Fuyunaga
Wife: [Formal] Daughter of Kujō Tanemichi
Children: Miyoshi Yoshitsugu (adopted by Miyoshi Nagayoshi), Masayuki, Matsura Magohachirō
Adopted Children: Masayasu (second son of Miyoshi Jikkyū)
Sogō Kazumasa served as a bushō during the Sengoku period. He was a retainer of the Miyoshi clan.
In 1532, Kazumasa was born as the fourth son of Miyoshi Motonaga at Shōzui Castle in Awa Province. His older brothers included Miyoshi Nagayoshi, Miyoshi Jikkyū, Atagi Fuyuyasu, and a younger brother named Noguchi Fuyunaga.
Sogō Kageshige, the lord of Sogō Castle in Sanuki, had a designated heir, Sogō Kanamitsu, who died early in life, so, upon orders of Nagayoshi, Kazumasa was adopted by Kageshige and inherited the headship of the Sogō clan.
In the sixth month of 1549, Kazumasa contributed to a victory against Miyoshi Masanaga (his father’s archrival) at the Battle of Eguchi in Settsu Province. This resulted in a collapse of the governance of Hosokawa Harumoto and the founding of Nagayoshi’s administration. In 1550, at the Siege of Nakao Castle, he stopped Harumoto from making a revival in Kyōto. In the sixth month of 1553, he collaborated with his second oldest brother, Jikkyū, in the killing of Hosokawa Mochitaka at the Kenshō Temple in Sanuki in an event known as the Shōzui Incident. In 1558, Kazumasa participated in the Battle of Kitashirakawa. In 1560, he routed Hatakeyama Takamasa in battle and was appointed by Nagayoshi as the lord of Kishiwada Castle. Thereafter, he continued to contribute on the battlefield in clashes across the Kinai, providing military support to his older brothers.
However, on 3/18 of Eiroku 4 (1561), he fell ill and died in Izumi Province where he was residing as a guardian for his son, Matsura Nobuteru. Kazumasa was was thirty years old. His natural son, Yoshitsugu, had been taken away by Nagayoshi and inherited the headship of the Miyoshi clan so he adopted his nephew (the second son of Jikkyū) named Sogō Masayasu, who then inherited the Sogō clan. Another son, Sogō Masayuki, was an illegitimate child, so he did not inherit the family and, instead, served as the chief retainer of Masayasu.
Cause of death
Kazumasa’s cause of death is cited as syphilis. Nevertheless, when he died, Matsunaga Hisahide, an individual with whom Kazumasa did not get along well, was at his side, giving rise to rumors in Kyōto at the time that Kazumasa had been assassinated by Hisahide.
According to a story in two historical accounts, around 1560, Kazumasa fell ill. While Kazumasa was convalescing with Hisahide at the Arima hot springs in Settsu, Hisahide noticed the ash-colored horse that Kazumasa was riding and told Kazumasa that Arima Gongen did not like ash-colored horses, so he should not ride that horse. Having a dislike for Hisahide, Kazumasa ignored him and continued riding the horse, whereupon he fell from the horse and ended on the verge of death.
With respect to this story, historians question whether Kazumasa could ride a horse while ill, or, given his courage and horse-riding skills, whether he would fall from a horse. In any event, Kazumasa died in the third month of 1561 so this story is inconsistent with the timing of his death.
On one occasion during battle, Kazumasa incurred an injury to his left arm. This would usually result in departure from the battlefield to recuperate, but Kazumasa rubbed salt into the wound as an antiseptic and wrapped the wound with vines from a wisteria tree in lieu of bandages before heading back to the battle to fight furiously with his spear. As a result, Kazumasa was called “Demon Sogō” and feared by his enemies. His courage also made him popular among his retainers while his hairstyle was called the “Sogō Head” with many emulating him.
Kazumasa provided a lot of support to his older brothers with respect to military affairs, so his death had an adverse effect on the military capabilities of the Miyoshi army.
Kazumasa did not get along well with Matsunaga Hisahide.
Matsunaga Teitoku assessed Kazumasa to be brave based on comments heard from Kujō Tanemichi, a master of haiku, that Sogō was a brave son-in-law.
Descendants of Kazumasa continue to the present day as the Sogō family.