Kashoku was a hereditary job or position or official post (and progression pass). Similar terms are Kado, Kagyo, but Kashoku has the national or official approval and control of the privilege and had an aspect of voluntary work for the authority.
The concept of hereditary occupations existed from the time of the Shisei system, and even in the Ritsuryo system (a system of centralized government based upon the ritsuryo code), there were cases where families that had passed on techniques and knowledge down the generations had priority in obtaining technical official positions. In addition, for academic official positions such as Hakaseke of the Daigaku-ryo (Bureau of Education under the ritsuryo system) had cases were Hakase came from the same family for generations. However, in these cases, it was important that the actual techniques and knowledge were passed down, but if such techniques had declined, passing down the position was difficult even for a descendant of a hereditary family.
In the eleventh century, the government office contract system was established and central government official jobs were held by certain clans. For example, Benkankyoku of the Daijokan (Grand Council of State) was held by Ozuki clan and the Gekikyoku (Secretaries' Office of the Council of State) was held by the Nakahara clan. In the same way, technical and academic official positions were also held by certain clans such as the Kamo clan and Abe clan of the Onmyoryo (Bureau of Divination), Sugawara clan and Oe clan of the Daigakuryo Kidendo (the study of the histories) (Bunsho hakase) with the background of the establishment of Kagaku.
Furthermore, in the twelfth century, the management and accompanying profit of Kanji and Kanjiryo that was maintained as the funds for the job (Kangaryo) began to be privately owned by the hereditary clans as part of the job system including the position itself and used as 'Chigyo (enfeoffment).'
In the same way, the highest position for the aristocrats, Sekkan, was hereditarily passed among the Mido branch within the Fujiwara clan, Northern house, Kujo branch and this branch monopolized the position as the chief of the Toshi and associated Kangakuin and denka no watari-ryo (the land which the Fujiwara family hereditarily succeeded). Furthermore, as the aristocratic society was restructured during the cloistered government, promotion path to official positions and the final achievable position/rank became determined more by birth, and the aristocratic clans from the ancient times differentiated into each mon and transformed into the "Ie (family, house)" of the middle ages. The mongyo that a mon had became kagyo that was passed down the ie, in other words, transformed into Kashoku. During the thirteenth century, the Sekkan position was passed in turn among the heads of the five families determined by paternal succession among the Mido branch, in other words, the Gosekke (five top Fujiwara families), became systemized. A system of relatively stable Kasho and position promotion path for the head of one or several families depending upon the family class became established as a system for every layer of the aristocracy. The establishment of 'Ie' was also seen among the resident landowner class and the parent-child inheritance of 'shoku (occupation)' accompanied by rights was commonplace.
The court of the middle ages was maintained by establishing Yusokukojitu (precedent cases and stories about court protocol) of Chogi as a Kagaku and the various aristocratic families became in charge of it as Kashoku and if the family had no successor, such families were reestablished by taking members in by adoption. However, with the collapse of court finances after the Onin War, Chogi was terminated and many aristocratic families were not reestablished once they had no successors. On the other hand, for buke (military class) and resident landowners, the concept of 'Ie' became recognized as the basic unit of ordinary society during the Sengoku period after the Onin War.
With this, the Toyotomi government which unified Japan used Kashoku of the aristocracy, military, officials and public as a method of maintaining civil order. Towards the aristocracy, the 'On okite tsuika (additional regulations)' in 1595 ordered diligence towards their Kashoku and Kogi as mandatory in exchange for guaranteeing or increasing land. On the other hand, the government reinforced Taiko-kenchi (the land survey by Hideyoshi TOYOTOMI) and Katanagari (sword confiscation) on the public and asked it to devote itself to Kashoku. The Tokugawa government followed and reinforced this approach and issued the 'Kinchu narabini kuge shohatto' (a set of regulations that applied to the emperor and the Kyoto nobles) for the aristocracy and reconfirmed and guaranteed the promotion path accompanying Kashoku and made it clear that the Tokugawa shogun family itself would make the shogun position as its Kashoku. In addition, for the buke and public, the government considered devotion and maintaining each family's Kagyo (family business) as their Kashoku and made this widespread throughout society to make this a method of controlling class and maintaining societal order. Furthermore, religious persons and craftsmen were to come from specific aristocratic families and temples (Inke) for which it was Kashoku. Documents such as "Hagakure (The Book of The Samurai" (bushi), "Choninbukuro" "Moanjo"(monk) encouraged people that staying and succeeding in their Kashoku/Kagyo was a societal responsibility.
After the establishment of the Meiji government, with the aim of the modernization of national management systems and utilizing human resources, the court system of hereditary positions held by the aristocracy was considered as an 'evil old custom.'
The Meiji government tried to separate the court and government and proceeded in taking away the class restrictions that were already starting to become fluid and allowed the public to have the right to select an occupation. Upon the ratification of the Constitution of the Empire of Japan, Hirobumi ITO wrote in the "Kenpo Gikai" that the custom of 'officials affiliated with an Ie and passing down positions amongst their clan,' in other words, Kashoku, was against the rights and obligations of the people.
The nineteenth article of the Constitution of the Empire of Japan states 'Japanese citizens can equally be appointed as administrative/military officials and other official positions according to the criteria determined by law.'
However, in actuality, the Kazoku (peerage) system had elements of Kashoku, and dukes and marquis were in principle eligible for a seat in the Kizokuin. Under the influence of the Ie system, the maintenance of Kagyo continued to be prioritized among the public and this could be considered as a relic of Kashoku.
Currently, the fourteenth article of the Japanese Constitution clearly negates the concept of Kashoku. The only position that could be considered as recognized by the nation is the Emperor, who is not guaranteed the same human rights as a citizen.
However, if the Emperor is considered as the sovereign, it would be difficult to consider the position of Emperor as 'shoku (occupation).'