Chakuryu refers to the direct line of descent from a clan. It mainly denotes the line of descent succeeded by the eldest son, or the chakunan (the eldest son and heir), of the soryo (head of a clan) and his legal wife. It is also called the seiteki (the eldest son of the legal wife), the chokkei (direct descent), the seikei (legitimate line), or the chakukei. The antonym of the word is the shoryu (line of a branch family). The chakuryu is also referred to as the 'gochakuchaku no kakei' to pay more respect. The chakuryu's family is called the soke (head family), the chakke (legitimate family), or the honke (main family).
What is chakuryu?
In ancient times and during the medieval period when the blood line of a clan was highly regarded, the order within the clan was maintained mainly by the ujinochoja (head of a clan). Although the authority of the ujinochoja sometimes temporarily declined during the medieval period, the Imperial Court granted the ujinochoja the privilege of ujinoshaku that allowed them to recommend candidates within their clans for the ikai (Court rank).
Under such circumstances, the position of the ujinochoja was handed down from the ujinochoja to their descendants; there were two types of succession, the 'clan succession' and the 'chakuryu succession.'
The former was an old succession system, where the basic idea was to let the person with the highest rank within a clan assume the position of ujinochoja. According to the ritsuryo code (criminal and administrative codes), being the chakunan was a criterion for the oni (granting of the ikai to a son of a man with Court rank), but never a requirement for the succession of ujinochoja. However, even a clan member from a branch family had a chance to become ujinochoja as long as he held the highest rank. But the latter system, which came into existence in the late Heian period, let chakunan of legal wives take over as ujinochoja from generation to generation. This minimized the risk of dispersing their fortunes and ranks; chakuryu, who held nobility and legitimacy of blood, were those who could advance the status of their clans and were greatly favored over the shoryu in terms of official ranks, for example.
This is not to say, however, that the succession system momentarily changed from 'clan succession' to 'chakuryu succession.'
The 'chakuryu succession' started among the samurai society first in terms of preventing the shoryo (territory) from being scattered, and it was not until the late Kamakura period that the basis of the system was realized by the whole society.
The Fujiwara clan, Court nobles who monopolized the management of the dairi (Imperial Palace), assumed the position of the sekkan-ke (family line of regents and chief advisors to the Emperor) by letting the family lines of FUJIWARA no Michinaga monopolize the positions of Sessho (regent) and Kanpaku (chief adviser to the Emperor), thus establishing the gosekke (the five sekkan-ke) of the Konoe family, the Kujo family, the Nijo family, the Ichijo family, and the Takatsukasa family led by the Konoe family, the chakuryu of the clan. However, 'clan succession' and 'chakuryu succession' coexisted among the sekkan-ke originating from the old clan, preventing one family of the gosekke from monopolizing the position of chakuryu.
Among the samurai class, however, MINAMOTO no Yoritomo, a descendant of the Kawachi-Genji (Minamoto clan) who rose as the leader of samurai, called himself chakuryu of the Minamoto clan, established the Kamakura bakufu (Japanese feudal government headed by a shogun), and established the basis of samurai government mainly led by the monyo (clans basically connected by blood) of his clan members and prominent gokenin (shogun's vassals). Mainly because of his uniting power as chakuryu of the Minamoto clan, Yoritomo was able to preside over the descendants of the same Minamoto clan such as Yoshikane ASHIKAGA and the Kai-Genji and dominate his cousin MINAMOTO no Yoshinaka, his uncles of MINAMOTO no Yoshihiro (Master Saburo SHIDA), and MINAMOTO no Yukiie, and MINAMOTO no Yoshishige, and Masayoshi SATAKE of the same clan.
The Hojo clan, who also held the reins of the Kamakura bakufu, dominated the important positions of the bakufu, and yet, the position of Shikken (Chief of Staff to the shogun) was succeeded mostly by the Tokuso (the patrimonial head of the main branch of the Hojo clan) except for a few examples; the position of the chakuryu used to succeed the position of the soryo was highly valued.
Since the Muromachi period, the soryo system (a system in which the shoryo of a clan were inherited by clan members, but they and their shoryo were ruled by the soryo) was gradually enhanced; the family line of chakuryu formed the soke and honke, and the shoshi-ke (families other than the chakuryu in a clan) as shoke (branch families) were integrated as its vassals, in some cases. The shoryu, however, were given a certain level of individuality and some shoryu attempted to be independent from or publicly opposed to the chakuryu; furthermore, there were even those who tried to usurp or overthrow the soke. The Sengoku period (period of warring states), in particular, was a time based on merit when bloodline did not guarantee rank or power; the Hosokawa clan, the shoryu, took power as the kanrei (shogunal deputy) from the Ashikaga Shogun family, the chakuryu of the Ashikaga clan who established the Muromachi bakufu; and the Amago clan, the shoryu, usurped the position of Shugo (Provincial Constable) from the Kyogoku clan, Izumo Shugo, and the chakuryu.
Since the Edo period when Ieyasu TOKUGAWA established the Edo bakufu, however, the position of chakuryu was emphasized again because the Tokugawa Shogun family highly valued choyo no jo (Confucian teaching regarding the relationship between senior and junior). The values and concepts of chakuryu no longer exist in the daily life of today's Japan, and yet there is a strong tendency to consider the family's religious services and the continuation of the family name mostly in terms of honke and the eldest son.