Suino was the officer of Kurododokoro (the Chamberlain's Office) and was in charge of all of general affaires including the receipts and disbursement of the treasury of Kurododokoro. In the Edo period, Suino oversaw the jigenin (court officials who were not allowed access to the palace) of Kurodogata (another name for Kurododokoro), and as Jigekekanjin (officials came from the families which were not allowed to enter the palace), he was called 'Saikanjin' along with Kyokumu (the chief secretary) of Benkankyoku (Controllers' Office) and Kanmu (chief secretary) of Daijokan (Grand Council of State).
The prescribed number of personnel for this post was three during the Heian period and in addition to the receipts and disbursements jobs for Kurododokoro, Suino also drafted the documents of Kurododokoro, such as cho (official certificate), kudashibumi (document issued by a superior or office) and hensho (letter of receipts), and signed these documents together with Kurodo (Chamberlain). Since the knowledge and skill of clerical work are required for this post, persons who learned Myobodo (study of Codes) or experienced civil officers in government offices were usually appointed to this position. Also, persons who were recommended by influential persons were often nominated. After his abdication, the Emperor Uda ordered the secretary of Goin Palace to compile records of disbursement while he was on the throne, and as seen from this fact, Suino had a close relation with the emperor. During the era of Emperor Horikawa, however, Suino were under restraint since they were regarded as 'arrogant' since they presided over everything instead of Kurodo. Since then, the Suino family was restricted to being placed in miscellaneous jobs and jigenin were appointed to the position. Since the end of Heian period, persons from the Hirata family of the Nakahara clan line were often appointed to this post, and in the late stages of the medieval times, this post became a hereditary post of the Hirata family, though some persons of other families such as the Abe family were appointed in the meantime. Persons of the Hirata family inherited the post until the Meiji Restoration.
Suino, who were once deprived of many jobs, resumed doing jobs of Kurododokoro together with the decline of the structure of the Imperial court. As "Kinpisho" (a book written by Emperor Juntoku, which records the history and origin of imperial court ceremonies and sets forth the rules and etiquette for carrying out such ceremonies) described Suino as 'Kurodogata Issaibugyo' (the head of Kurodogata), Suino played a big role in the management of Kurododokoro and was involved in many jobs at the Imperial court.
Oritada HIRATA, who studied Hidetaka FUNABASHI and was known as the expert of Yusoku kojitsu (court and samurai rules on ceremonies and rites), was appreciated by the Emperor Goyozei for his talent and was allowed access to the retired emperor's palace, though it was a rare case for jigekanjin. The Edo bakufu (Japanese feudal government headed by a shogun), which had just been established at the time, intended to control the Imperial court by engaging in the restoration of the well-ordered Imperial court. The intentions by the bakufu coincided with the Imperial court's intention to restore Imperial ceremonies, and the system of jigekanjin was revised accordingly. As a result, Kyokumu Oshikoji family, Kanmu Mibu family and Suino Hirata family became responsible for various clerical and administrative jobs relating to ceremonies under the instruction of bugyo and shikiji (the head of office) while commanding the jigekanjin of Gekikata (Secretaries' Office), Kangata (one of government office) and Kurodogata respectively ('Kinchu Shosei Shoshi to Sahonokoto' (manners in political affairs and officers of the Imperial Court)). As a result, Suino came to control the jigekanjin of about 60 families, including those of Zushoryo (Bureau of Drawings and Books), Mondo no tsukasa (Water Office) and Kuraryo (Bureau of Palace Storehouses), in addition to those of Kurodo dokoro. Also, chigyodaka (a stipend in terms of the rice production of the fief) of the Hirata family was raised to 31 koku (about 5,580 liter) and it became the third-ranking jige family.
Behind the scenes of the above reform, the bakufu and high-ranking people of the Imperial court seemed intent to restore the Imperial court and realize its effective management by restricting the monopolistic rule over jigekanjin by Kyokumu Oshikoji family and Kanmu Mibu family, which exclusively ruled jigekanjin for a long period and were called 'Ryokyoku' or 'the leader of jigekanjin.'
Since then, the posts of Kyokumu, Kanmu and Suino became hereditary posts, and persons appointed to these posts were called Saikanjin who were supposed to command jigekanjin under their respective jurisdiction.
In terms of treatment, however, the Hirata family was treated as a family that was inferior to Kyokumu Oshikoji family and Kanmu Mibu family which were called 'Ryokyoku.'
After the Meiji Restoration, while both Oshikoji and Mibu families were conferred Baron, the Hirata family was treated as shizoku (family with samurai ancestors) equally with other government officials. Being jigekanjin, however, Suino's authority in practical jobs was equivalent to that of Kyokumu and Kanmu. At present, a common view of the researchers of the early-modern times Imperial court is that the status of jigekanjin at that time was 'Sansai' (literally, three officials) structure led by the three Saikanjin families of Kyokumu, Kanmu and Suino.