Lifespan: Entoku 1 (1489) to 6/10 of Eishō 17 (1520)
Rank: bushō, shugo daimyō
Title: Master of the Western Capital Office
Clan: Awa-Hosokawa → Hosokawa-Keichō family
Bakufu: Deputy shōgun of the Muromachi bakufu, Military Governor of Tanba, Settsu, Sanuki, and Tosa provinces
Father: Hosokawa Yoshiharu
Adoptive Father: Hosokawa Masamoto
Siblings: Yukimochi, Sumimoto, sister (wife of Hosokawa Masakata)
Wife: [Formal] Seitaiin
Children: Harumoto, daughter (formal wife of Hatakeyama Yoshitaka), daughter (formal wife of Arima Shigenori)
Hosokawa Sumimoto served as a bushō and shugo daimyō. Sumimoto was the thirtieth deputy shōgun of the Muromachi bakufu and the military governor of Tanba, Settsu, Sanuki, and Tosa provinces. He served as the fourteenth head of the Hosokawa-Keichō family – the main branch of the Hosokawa clan.
After battles with Hosokawa Takakuni known as the Conflict between the Hosokawa (Ryō-Hosokawa no ran), he assumed the position of deputy shōgun and temporarily formed a political administration, but after a short period this collapsed while Takakuni usurped his role as the deputy shōgun. Earlier, Sumimoto’s adoptive father, Hosokawa Masamoto, had designated Sumimoto as his successor, but Sumimoto did not wield any of the power of the deputy shōgun.
Sumimoto was born to Hosokawa Yoshiharu (the younger brother of Hosokawa Yoriyuki and descendant of Hosokawa Akiharu), a member of a branch of the Hosokawa clan. Yoshiharu served as the military governor of Awa Province in Shikoku and died when Sumimoto was six years old, so Sumimoto was raised by his grandfather, Hosokawa Shigeyuki.
Sumimoto was a member of the Awa-Hosokawa family, a branch of the Hosokawa clan, at the level of a shōbanshū, or an attendant to the shōgun. Meanwhile, Hosokawa Masamoto, the head of the Hosokawa-Keichō family, had influence as the deputy shōgun of the bakufu, but remained unmarried and without a child, so he adopted Sōmeimaru (later known as Hosokawa Sumiyuki) from the Sekkan-Kujō family to be his designated successor. However, Masamoto did not get along well with Sōmeimaru, so, in 1503, he removed him from the line of succession and, instead, adopted Rokurō (later known as Hosokawa Sumimoto) to be his heir. That same year, Masamoto held a coming-of-age ceremony for Rokurō and gave him the name Sumimoto with one of the characters in his name from Ashikaga Yoshizumi, the eleventh shōgun, and the other character from his own name, indicating his position as the designated successor to the Keichō family. From 1506 to 1507, Sumimoto joined Sumiyuki to attack and defeat Isshiki Yoshiari in Tango Province.
The Eishō Disturbance
Although Sumimoto was the designated heir of Masamoto, after adopting Sumimoto, Masamoto then adopted Hosokawa Takakuni. Takakuni was the natural son of Hosokawa Masaharu of the Yashū branch of the Hosokawa clan. Consequently, Masamoto adopted three sons who were his potential heirs：Sumuyuki, Sumimoto, and Takakuni. In the summer of 1507, Masamoto was assassinated by supporters of Sumiyuki, including Kōzai Motonaga and Yakushiji Nagatada in the Lord Hosokawa Incident. This gave rise to a prolonged succession struggle known as the Eishō Disturbance that was not finally settled until 1531 when Sumimoto’s son, Hosokawa Harumoto, defeated Hosokawa Takakuni at the Collapse at Daimotsu. The day after the assassination of Masamoto, Sumimoto was also attacked at his residence by retainers of Sumiyuki, whereupon he fled with Miyoshi Yukinaga to Aochi Castle in Ōmi Province. The men escaped with the assistance of Yamanaka Tametoshi of Kōka. Several months later, Sumimoto drew on the support of kokujin in Ōmi to launch an attack in Kyōto, killing Sumiyuki and his supporters. The following day, Sumimoto had Ashikaga Yoshizumi, the shōgun, recognize his succession to the Hosokawa-Keichō family.
Nevertheless, Sumimoto was young at this time, while Miyoshi Yukinaga acquired more influence in his position as the kasai, or head of house affairs. This led to conflict between Sumimoto and Yukinaga whereby Sumimoto attempted for a while to return to Awa Province, but was finally dissuaded by Ashikaga Yoshizumi. He then dispatched a retainer named Akazawa Nagatsune to Yamato and imposed his control over the province.
At this time, Ashikaga Yoshitada (formerly Yoshiki and later known as Yoshitane) resided in Suō Province where he took refuge after serving as the tenth shōgun. After Yoshitada learned of these internal conflicts in Kyōto, he commenced a march upon Kyōto with the support of Ōuchi Yoshioki, the sengoku daimyō based in Yamaguchi in Suō. Sumimoto made plans for a reconciliation with Yoshioki, but this fell apart after Hosokawa Takakuni switched allegiance to the Ōuchi. Takakuni, one of the adopted sons of Masamoto, had earlier cooperated with Sumimoto in the attack against Sumiyuki.
The Conflict between the Hosokawa
In the spring of 1508, Takakuni commenced an invasion of Kyōto. Itami Motosuke of Settsu, Naitō Sadamasa of Tanba, and Hatakeyama Hisanobu of Kawachi acted in concert with Takakuni, defeating Sumimoto. Soon thereafter, Sumimoto, Yukinaga, and Ashikaga Yoshizumi fled with the assistance of Yamanaka Tametoshi to Ōmi. In the summer, Ashikaga Yoshitada marched upon Kyōto with the support of Ōuchi Yoshioki, restoring the position of Yoshitada as shōgun and taking away Sumimoto’s succession of the Keichō family in favor of Takakuni. Meanwhile, Akazawa Nagatsune, a retainer of Sumimoto, was killed in Yamato by Hatakeyama Hisanobu.
Despite regaining his position as shōgun, Yoshitada began to have conflicts with Ōuchi Yoshioki. In 1509, Sumimoto and Yukinaga attacked Kyōto, but lost in a counterattack by Takakuni and Yoshioki at the Battle of Nyoigatake, causing Sumimoto and Yukinaga to flee to Awa.
In 1511, Yoshizumi joined with his brother-in-law (Hosokawa Masakata – head of the Tenkyū branch of the Hosokawa) on a series of attacks. This began with an assault against Fukai Castle at the Battle of Fukai in Sakai in Izumi Province. Thereafter, the combined forces of Akamatsu Yoshimura and Hosokawa Hisaharu attacked Takao Castle at the Battle of Ashiyagawara in Settsu Province. Next, Sumimoto and Masakata, together with Akamatsu Yoshimura, attacked the allied forces of Takakuni and Ōuchi Yoshioki at the Battle of Funaokayama in Kyōto. However, prior to this conflict, Yoshizumi died of illness, and the forces suffered a major defeat by the Ōuchi. Masakata was killed while Sumimoto escaped to Settsu.
In 1518, Ōuchi Yoshioki returned to his home province of Suō. In 1519, Sumimoto and Yukinaga invaded Settsu at the Siege of Tanaka Castle. Early in 1520, locals rioted in Yamashiro Province in concert with Sumimoto, while Ashikaga Yoshitane, the shōgun, began to collude with Sumimoto. This left Takakuni isolated, whereupon he fled to Sakamoto in Ōmi Province, enabling Sumimoto to establish a new administration. However, by the spring of 1520, Takakuni had re-grouped his army and attacked Kyōto. Sumimoto and Yukinaga did not have time to gather forces, resulting in the defeat of Yukinaga at the Battle of Tōji Temple, at which he was apprehended and killed himself. Sumimoto fled to Tanba Castle in Settsu, and his administration collapsed after a brief tenure. Sumimoto became depressed and fell ill, and under continuing attack by Takakuni, was forced to flee again to Harima Province. He later died at Shōzui Castle in Awa.
Following his demise, Sumimoto was succeeded by his eldest son, Hosokawa Harumoto. Harumoto joined with Miyoshi Motonaga (the grandson of Yukinaga) and sailed to the Kinai Region. Harumoto and Motonaga defeated Takakuni in a pincer attack at the Collapse at Daimotsu, after which Takakuni was captured and forced to kill himself. However, battles continued against Takakuni’s adopted son, Hosokawa Ujitsuna. In this midst of this conflict, Motonaga’s son, Miyoshi Nagayoshi, sided with Ujitsuna, causing Harumoto to lose. His descendants became elders of the Miharu domain of Mutsu Province in the Edo period via connections with the Toyotomi family.