Kanrei is the name of a post in the Muromachi bakufu (Japanese feudal government headed by a shogun). Originally a word meaning to manage/rule an official post or fief, the regent to the Kamakura bakufu was sometimes called Kanrei.
Throughout the Muromachi period, the three families who were appointed to Kanrei, the Shiba, Hatakeyama, and Hosokawa clans, along with the four families that were appointed to Samurai-dokoro tonin (Governor of the Board of Retainers), were collectively referred to as "Sankan shishiki."
Originally filling a secretarial role in the management of the Ashikaga clan, it started as a steward who administered the mechanisms of feudal rule. The military government that Takauji ASHIKAGA established in support of the Northern Court (Ashikaga Shogunate, Muromachi bakufu) had dual governing authorities that Takauji's younger brother, Tadayoshi ASHIKAGA, was in charge of, and KO no Moronao, Yoriaki NIKI and Kiyouji HOSOKAWA worked as stewards of the Shogunate. At the time of Yoshiakira ASHIKAGA, the second Shogun, because of instabilities such as Kiyouji HOSOKAWA falling from grace due to internal disputes in the Shogunate, Yoshiakira briefly conducted direct Shogunal rule. In the period of Yoshiakira the role of Hikitsukeshu (Coadjustor of the High Court) who administered regional governing authorities was reduced and the power of the stewards was strengthened, with the aim of establishing a centralized governing authority.
In 1362, the 13 year old Yoshimasa SHIBA was appointed, and his father Takatsune SHIBA was his guardian. In 1366, in the Joji Incident spurred by the anti-Shiba Doyo SASAKI, the Shiba clan fell, and Yoriyuki HOSOKAWA, who had the support of Doyo and the others, became steward. It is thought that the transition from steward to Kanrei was between Kiyouji and Yoriyuki. Afterward, the Kanrei supervised government affairs, and management of the Ashikaga Shogun family was transferred to Mandokoro (Administrative Board). Yoriyuki HOSOKAWA fell in the Koryaku Coup, and Yoshimasa SHIBA was rehabilitated, but even after that the Shiba and Hosokawa clans were opposed over the Kanrei position. In 1398, Motokuni HATAKEYAMA became Kanrei, and after that the Shiba, Hatakeyama and Hosokawa Keicho families related to the Ashikaga family were appointed in turns.
Personnell affairs and contents that passed assessment were written on Kanrei stationary and dispatched to the various provinces. At the time of the third Yoshimitsu ASHIKAGA and the fourth Yoshimochi ASHIKAGA, there was a conference system centered around the Shukuro (chief vassal), and the position of Kanrei was lowered; and the Shiba family first declined, not least because of financial burdens. The sixth Shogun, Yoshinori ASHIKAGA, aimed to strengthen the authority of the Shogun, so the authority of the Kanrei was reduced, and intervened in disputes over inheritence in the Shiba and Hatakeyama clans, which later contributed to the decline of both families.
In the Onin War, which occurred during the time of the eighth Shogun, Yoshimasa ASHIKAGA, at first the Kanrei Yoshikado SHIBA joined the Western Army commanded by Sozen YAMANA, Shogun Yoshimasa and the others were protected by the Eastern Army commanded by Katsumoto HOSOKAWA, and the Shogun and Kanrei in the Shogunate split. In 1468, Katsumoto HOSOKAWA, who commanded the Eastern Army, became Kanrei.
The power of the Shogun, as well as the Shiba and Hatakeyama families, declined steadily after the Onin War, with only the Hosokawa clan expanding its power; before long Katsumoto HOSOKAWA's son, Masamoto HOSOKAWA, established heredity of the Kanrei post for the Hosokawa clan, and eventually, in the Meio Coup, overthrowing the Shogun and siezing all of the Shogunate's authority (establishment of the Hosokawa Keicho administration). However, when Masamoto was assassinated by vassals over succession, the Hosokawa clan split and declined. In the 1500s, Yoshioki OUCHI, Nagayoshi MIYOSHI, Sadayori ROKKAKU and others ruled the Shogunate as deputy Kanrei, the post of Kanrei became merely formal. Then after Ujitsuna HOSOKAWA's death in 1563, it in fact came to an end through natural lapse.