Sobayonin (lord chamberlain) (側用人)
Sobayonin was a post in the bakufu and domains in the Edo period. The official post name was Osoba-goyonin.
Sobayonin in domains
The Sobayonin placed in domains was sometimes called Osoba for short. For lords, there were the public sphere and the private sphere, and Karo managed whole domain administration, while the Sobayonin managed the family affairs of the lord family and played a role of a secretary of the lord and his heir. However, the name and jobs of the Sobayonin were not universal, and importance of the post depended on the domain.
In the bakufu, the Sobayonin sometimes gained more power than Roju (the second highest post in the bakufu government or a person (s) in the post), but in domains, such an example scarcely existed. However, because of the characteristics of the post, a person from a low social standing family was often appointed to the Sobayonin post when he was a competent close confidant trusted deeply by the lord, so the load of the post was invariably heavy. In some domains, a Sobayonin officer was also provided with the title of Osoba-goyo-toritsugi, and in this case, the function of the officer was almost the same as those of a Sobayonin officer in the bakufu.
The Sobayonin officer in domains are generally selected from at least Kyujin (lower-ranked one of the upper class retainers) or upper class retainers ranked at moshitsugi (or toritsugi) (an official for conveying a message).
Furthermore, in many domains throughout the nation, heirs of senior retainers served as Kosho (pages) or Sobayonin officers when they were in the heyazumi status (living in their parents' houses) before inherited their family head positions
The Sobayonin post was mostly placed under the Yonin post, but in some domains, for example, the Mito domain and the Kaga domain, it was placed above the Yonin post. Compared to the Yonin post and the Banto post, the status level depended on the domain.
Sobayonin in the Edo bakufu
Sobayonin officers in the Edo bakufu were close confidants of seii taishogun (literally, "the great general who was to subdue the barbarians"), and played a role of informing Roju or other officers of instructions from Shogun. A rice yield of 10,000 koku (approx. 180 liters/koku) was given to the post. Famous Sobayonin officers were Yoshiyasu YANAGISAWA in the era of Tsunayoshi TOKUGAWA, the fifth shogun; Akifusa MANABE in the eras of Ienobu TOKUGAWA, the sixth shogun and Ietsugu TOKUGAWA, the seventh shogun; Tadamitsu OKA in the era of Ieshige TOKUGAWA, the ninth shogun; Okitsugu TANUMA in the era of Ieharu TOKUGAWA, the tenth shogun; and Tadaakira MIZUNO in the era of Ienari TOKUGAWA, the eleventh shogun.
In the early Edo period, officers in this post, called kinju shuttoyaku (an attendant to Shogun) at that time, were selected from 5000-koku class hatamoto (direct retainers of the bakufu) who were involved in important affairs as close aides of Shogun, and in particular, played a role of relaying important matters. After becoming the fifth shogun, Yoshitsuna made Narisada MAKINO, who was Karo (chief retainer) of the Tatebayashi domain at that time, succeed the former kinju shuttoyaku post as the newly named 'Sobayonin' post, converting his status to Fudai daimyo (a daimyo who had belonged to the Tokugawa group before the Battle of Sekigahara), and made him handle important matters, preparing for dictatorship.
In 1684, Masatoshi HOTTA, Tairo (the highest post in the bakufu government to the person in the post) was slain with a sword in the Edo castle by Masayasu INABA, his cousin and a wakadoshiyori officer. This incident led the goyobeya room (office room) of Roju to be moved to a place far away from the residence of the shogun, in the pretext of worrying about his safety. Therefore, power of the Sobayonin officer, who mediated between the shogun and the Roju and played the role of relaying instructions from shogun to Roju, increased suddenly. The politics style which the government was operated by Sobayonin rather than by Roju was called 'Sobayonin seiji' (Sobayonin-based politics) by historians in later eras. Shogun exercised dictatorship through the Sobayonin officer, and the officer came to be used by Shogun as a means of containing power of Roju.
After Narisada MAKINO retired, Tsunayoshi appointed Yoshiyasu YANAGISAWA, who had been MAKINO's close aide since MAKINO was Karo of the Tatebayashi domain, and showed more favor to Yoshiyasu than to Makino. In addition, around this time, Tsunayoshi started losing enthusiasm for politics, and the intention of Yanagisawa was sometimes conveyed as that of the shogun. Furthermore, it became custom that the Sobayonin officer could refuse a matter which Roju requested to relay to the shobun but the Sobayonin officer was against it. Although having never been appointed to Roju, Yanagisawa was given Kamiza (seat of honor) of Roju and the title of Roju-kau (Roju level), occupying the highest post of the bakufu government both in name and reality. Although no such a title was provided for Akifusa MANABE in the next generation, he possessed more power than Roju accutually. In the Tsunayoshi era and later, the bakufu operation was conducted mainly through Sobayonin (or Goyotoritsugi), completing the political style called dictatorship by shogun.
The eighth shogun, Yoshimune TOKUGAWA, who adopted as his slogan 'Everything should be done as Ieyasu TOKUGAWA specified,' abolished this system, which did not exist when the bakufu started, immediately after he assumed the Shogun post, gaining the confidence of Fudai daimyo. However, he established the Osoba-goyotoritsugi post for relaying messages between Shogun and Roju to appoint Hisamichi KANO and Ujinori ARIMA, his confidants who accompanied Yoshimune from the Kishu domain and became retainers of the bakufu (Hatamoto), to the post, and operated the bakufu through them, retaining the 'Sobayonin seiji' effectively. However, Yoshimune did not make them daimyo immediately after appointing them to the new post, and did not permit them to deliver political remarks that were allowed for Roju nor to refuse relaying messages from Roju to Shogun.
When the ninth shogun,Ieshige, who is said to have suffered from speech disorder, became the ninth shogun, only his confidants who had been his attendantspersons could understand his ambiguous speech. Therefore, Tadamitsu OOKA, one of his confidants, became in charge of important matters, restoring the sobayonin system. However, Ieshege and Ieharu, the shogun who succeeded the Ieshige, did not want to be involved in political matters actively, therefore, it can also be said that the Sobayonin officers, such as OOKA and Okitsugu TANUMA, came to have strong power naturally. Of them, Tanuma was the first person who officially assumed Roju from Sobayonin through Roju-kaku.