Kafu (family tradition) is a style of behavior, including custom and procedure, which has been specifically inherited down the generations within certain individual families.
Ever since the clan system was established in ancient Japan, it has been deemed to be most important for those people in the upper class, especially in the families called honke (the head family) or chakuryu (the main branch of the family) to maintain and succeed for generations the line, status, rite, business, properties, kamon (family), and trade or profession of the family. For that purpose, certain customs and procedures of each family were formed and maintained and were gradually nurtured as kafu. Therefore, the written code of family tradition, which was called kakun (family motto), kaken (family code) or kaho (family rules), had been prepared since the early days in those families including court nobles and warrior households and was regarded as the principle that should be followed by all family members headed by the family head.
In the Edo period, every daimyo (feudal lord) family under the shogunate system was said to have a firm kafu and kakun, and even among some merchants and peasantry families, kafu was established and kakun and kaken were prepared. In each daimyo family, the family head and all vassals including karo (chief retainer) and other retainers regardless of their rank believed that it was the proof of fealty to the family of their lord to respect and maintain kafu. On the other hand, when a person adopted from a different family succeeded a daimyo family, the new family head, who was used to the tradition of his family home, might possibly have not fitted into the kafu in the daimyo family he was adopted by, and he might have quarreled with the retainers to cause family troubles. Harunori UESUGI, who was adopted from the Akizuki family, had been told cautiously by the karo of his home Akizuki family not to be against the manner of the Uesugi family. Sadanobu MATSUDAIRA, who was adopted from the Tayasu family, had been told cautiously by the karo of his home Tayasu family not to invite antipathy from the people in the Hisamatsu-Matsudaira family by showing off the kafu of the Tayasu family.
In the Meiji period and later, along with the formation of several zaibatsu (company syndicates), kaken and kakun were known to be established in order to maintain the management mainly by the head family, including family members and executive officers. This was done regardless of whether the family was a shoka (mercantile house) since the Edo period or was a newly-emerging house in the Meiji period or later; it was said that the kafu in the Mitsubishi zaibatsu, in which the president had a strong power, the Mitsui zaibatsu, in which there was a strong relationship between the head family and the general manager (executive officer), and in the Sumitomo zaibatsu, in which the general manager (executive officer) was given an important post, was 'ifuku' (awe), 'kosho' (attendant of a noble person), and 'keiai' (to love and respect), respectively. The idea of kafu also penetrated through general families together with the notion of family system, and expulsion of a son's wife who expressed disobedience to her husband or in-laws was justified as a reason for divorce.
After the World War II, with the collapse of the family system and the trend toward the nuclear family being in progress, the idea of kafu has been changing and disappearing rapidly.