The Rokkaku clan (六角氏)
The Rokkaku clan was a samurai family (shugo guar feudal lord) descended from the Sasaki clan of Uda-Genji (Uda-Gen clan) and whose influence was centered in the southern part of Omi-no-kuni from the Kamakura era through the Sengoku period (Japan). There is no blood connection with the court-noble Rokkaku Family of Fujiwara-hokkeryu.
The Rokkaku clan is one of four branch families of the Sasaki clan called Omi-Genji (Omi Gen clan), and had ruled the entire area of Minami Omi as the shugo (guard) since the Kamakura era. It is said that they called themselves the Rokkaku clan because they had a house in Rokkakudo (Choho-ji Temple), Kyoto.
During the Kamakura period, the shogunate was particularly on the alert for the Sasaki clan, partly because most of the Sasaki clan had a history of belonging to the court's side in the Jokyu-no-ran War. After the death of Nobutsuna SASAKI, most of his territory was supposed to be inherited by his third son, Yasutsuna SASAKI; however, a move accepted by the shogunate after the appeal by Nobutsuna's disinherited first-born son Shigetsuna SASAKI, whereby the territory was divided into four on behalf of all Nobutsuna's sons. The fact that the Rokkaku clan (namely the Yasutsuna family) was the legitimate blood of the Sasaki clan remained unchanged, but the Rokkaku clan's power was seriously weakening. At the downfall of the Kamakura shogunate, Tokinobu ROKKAKU took the side of Rokuhara Tandai, a local commissioner, intending it to be to the end, but was defeated and forced to surrender.
The Rokkaku clan had been opposed to the Kyogoku clan, which originally belonged to the same family, since the Muromachi era when the Kyogoku clan was gaining power, and fought against the Kyogoku clan over the hegemony of Omi. Partly because Mt. Hiei-zan was within the territory, the regional rule had not been stabilized during the Muromachi era, and Mitsutsuna ROKKAKU and his son Mochitsuna ROKKAKU were forced to commit suicide due to the vassals' rebellion; thereafter, Hisayori ROKKAKU, who had inherited Mitsutsuna and Mochitsuna, committed suicide due to the strain of grief after the conflict with the Kyogoku clan. Kameju ROKKAKU, who is considered to be the family head after Hisayori (there are several theories over the identity of Kameju), belonged to the western army at the turmoil of the Onin War, and in the next generation that of Takayori ROKKAKU, the ninth-generation shogun Yoshihisa ASHIKAGA and the tenth-generation shogun Yoshitane ASHIKAGA sent a punitive expedition to Takayori in 1487. Takayori fought back against the invasion twice and further won the conflict with the Iba clan, which was the shugodai (delegated guard), thus becoming a warlord. Sadayori ROKKAKU, Takayori's second son, appeared at the start of the Sengoku period (Japan). Sadayori became the kanryodai (delegated lord) of the Ashikaga shogun family, was based at Kannonji Castle, and built power across Omi in order to foster the full blossoming of the Rokkaku clan. However, after the death of Sadayori, in the generation of Yoshikata ROKKAKU (who inherited Sadayori), the Rokkaku clan's power began to weaken due to various factors, including its defeat by Nagamasa ASAI at the Battle at Norada in 1560. In the generation of Yoshikata's son, Yoshiharu (Yoshisuke ROKKAKU), in 1563 the killing of his chief vassal Katatoyo GOTO and his son caused the Kannonji family feud--the infighting of the Rokkaku Family--which forced the signature of the Rokkaku Clan Act, at which the weakening of the Rokkaku clan became significant.
As mentioned above, the Rokkaku clan was greatly weakened during the period of Yoshikata ROKKAKU and his son, Yoshiharu, and in 1568 the clan was defeated by the Joraku army led by Nobunaga ODA, losing its territory. Thereafter, although Yoshitaka and Yoshiharu put up guerrilla resistance against Nobunaga, ultimately they fell. Later, the Rokkaku clan was accepted as vassal by Hideyoshi TOYOTOMI and Hidetsugu TOYOTOMI and again used the Sasaki cognomen to become Hatamoto (direct retainer of the shogun) during the Edo period.
The descendant of Yoshiharu's younger brother, Yoshisada ROKKAKU (who is said to have been given the title of family head by Yoshiharu after the Kannonji family feud, but there is another theory), also survived as Hatamoto during the Edo period. Yoshisada's descendant also used the original surname, the Sasaki cognomen.
Yoshiharu's younger brother, Koichi, became a vassal of Nobukatsu ODA, and Koichi's son Masakatsu used the Ikoma cognomen and became a chief vassal of the Oda Family in the domain of Uda Matsuyama. Masakatsu's descendant served the Oda Family, in the domain of Tanbakaibara.
The above is the conventionally accepted theory, but there is another theory which holds that the descendant of Ujitsuna ROKKAKU (the heir of Takayori and elder brother of Sadayori) survived under the aegis of Nobunaga, and that Yoshisato ROKKAKU (the old vassal of Yoshihide ROKKAKU, who was the father or elder brother, and the Kataimina (a name for a dead person)) served Hideyoshi TOYOTOMI to become a feudal lord of 120,000 koku, was given the Toyotomi cognomen and the title of palace staff and was consistently well treated, all of which has been the prevailing theory in modern times. According to this theory, Sadayori's bloodline was the Mitsukuri Family of the Rokkaku clan's branch family as just a jindai (role).