Matsugo Yoshi (末期養子)
The term "Matsugo yoshi" refers to a son who was adopted on his adoptive father's deathbed. During the Edo period, when a head of a samurai family, without a son to carry on the family name, was on his deathbed due to an accident or disease, a son was urgently adopted in order to prevent the extinction of the family name. Even when the head of the family had been already dead, sometimes an adoption was carried out in the name of the family head by concealing his death for some time. Such a practice is also called "Matsugo yoshi". However, as Matsugo yoshi was an emergency measure, if the family head managed to recover miraculously, he was able to cancel the adoption.
The circumstance concerning the prohibition and lifting a ban
During the early Edo period, the Edo bakufu (Japanese feudal government headed by a shogun) prohibited the daimyo (Japanese feudal lord) to carry out the practice of Matsugo yoshi. To take over as the reign of a samurai family, a successor was required to notify and to be approved as the heir and son by the head family beforehand (the family of the Tokugawa Shogun was the head family of all the daimyo families). Matsugo yoshi did not meet this requirement. A successor of a daimyo family whose rank was Omemie (a rank with the privilege to have an audience with one's lord or a dignitary) or higher had to have an audience with the Shogun before the adoption took place. The circumstance concerning the prohibition of Matsugo yoshi was as follows.
Primarily, it was difficult to confirm the will of the family head by that time the Matsugo yoshi was required. It was feared that retainers might assassinate the family head and replace him with someone convenient to their needs. But the most important purpose for the prohibition was in the bakufu's motivation to weaken the influence of daimyo in order to control them more easily. The banning of Matsugo yoshi was one such measure.
During the early Edo period when the control system had not been established yet, especially the period between the foundation of the bakufu and the regime of the third Shogun Iemitsu TOKUGAWA, many daimyo families became extinct due to the lack of an heir. This measure worked very well in establishing the shogunate system. On the other hand, the samurais who served the extinct daimyo families became ronin(the masterless samurai), which caused a social instability.
The most telling example of such a case was the Keian Incident of 1651, or so-called the Incident of Shosetsu YUI. The incident involved ronins who banded together in an attempt to overthrow the bakufu, and was a sign of the growing political unrest as a result of strict controls which the shogunate enforced on daimyos. In the earlier Shimabara War (1637 - 1638), many ronins participated in the uprising which made its suppression difficult.
For the circumstance described above, and together with the fact that the control system of the shogunate was considered complete and secure for the time being, in 1651, the shogunate lifted the ban on Matsugo yoshi. However, even after the lifting of a ban, for Matsugo yoshi to be given approval, the procedure of "Hanmoto Mitodoke", in which the family head was confirmed as alive and his will for adoption was certified by a bakufu official, had to be carried out, which made it not always as straightforward as it could have been.
(Later, however, the procedure in which the family head was confirmed as alive became a matter of formality.)
Additionally, it was decreed that the family head must be aged between 17 and 50 in order to be entitled for an adoption of Matsugo yoshi. A family head who fell outside this age bracket could not adopt a Matsugo yoshi. The permission for the adoption of Matsugo yoshi by family heads aged less than 17 was decreed in 1663, and the permission for those aged over 50 was decreed in 1683.