Born in Kyoto as a son of Hosokawa Katsumoto, the kanrei who led the eastern army in the Onin War. Born amid that war, he was raised as heir of the Hosokawa Keicho house. His mother is said to have been an adopted daughter of Yamana Sozen.
When his father Katsumoto died, he succeeded while still a child as head of the Keicho Hosokawa. In the last years of the Onin-Bunmei War, local rule depended heavily on retainers. He bore a kanrei house's weight from early on.
In the Bunmei years he came of age amid house and bakufu strife. Post-Onin Kyoto lay ruined, and the shogunal house was tossed by Hosokawa and Hatakeyama fights. Masamoto used force and intrigue to guard the kanrei house.
He became Muromachi kanrei and took part in bakufu politics under shoguns Yoshihisa and Yoshiki (Yoshitane). As a leading kanrei house the Hosokawa held power, and Masamoto wielded influence from Kyoto into the west.
When Ashikaga Yoshiki became shogun, Masamoto aided him as kanrei while steadily gaining power beyond the shogun. He joined campaigns such as against the Rokkaku and engaged deeply in Kinai war. The balance of shogun and kanrei was reversing.
He staged the Meio Coup, deposing shogun Yoshiki and installing Yoshizumi. As kanrei he held real bakufu power and showed that shoguns could be replaced. Some see this coup as the start of the Sengoku age.
A devout follower of Shugendo, he had no sons of his own and meant to pass the house by adoption. He took several adoptees—Sumiyuki, Sumimoto, Takakuni—and rival retainer bands around them later sparked major conflict.
After the Meio Coup he became so powerful he was even called a half-shogun. Yet he devoted himself to Shugendo and often left affairs to retainers; that arrogance and carelessness are seen as one cause of his assassination.
He pushed to make Hosokawa Sumimoto his heir, raising tension with other adoptees' factions. His authoritarian rule and the house split spread unease among Kyoto warriors and townsmen. Kanrei authority was still strong, so opponents could not move easily.
He was attacked and killed by Kozai Motonaga, Yakushiji Nagatada and others, sparking the Eisho Disturbance. Fighting among adoptees intensified, and Hosokawa and bakufu chaos deepened. It became an emblem of Sengoku Kyoto.
Yamana SōzenHosokawa KatsumotoHino TomikoHatakeyama MasanagaŌuchi Yoshioki
Asakura Takakage (Toshikage)Hosokawa KatsumotoŌta DōkanAshikaga YoshimasaAshikaga YoshimiHino TomikoHatakeyama MasanagaŌuchi Yoshioki
People of the Muromachi period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.