The 5th century was a century of wealth for the Yamato kings compared to the one before it. One evidence of the flourishing wealth of the kings was the increasing number of royal estates being established by the Yamato court.
A royal estate was a piece of land (including the inhabitants, buildings and produce from it) that was regarded by law as belonging to a Yamato king as a hereditary right.
Early royal estates were located mainly in and around the Nara plain and were administered directly by the Yamato court. Nihon shoki mentions that King Keiko in the 4th century had been granted the Yamato royal estate while he was crown prince. This was confirmed to be fact from archaeological digs that indicated that the estate was located in the present-day village of Miyake in the Shiki District of Yamato in the area where huge burial mounds were built during the 5th and 6th century. Later royal estates were established in outlying districts and distance provinces extending the control of the Yamato court and state. By establishing royal estates, a king could hope to increase his revenues and income.
The rebellion in Kyushu
In northern Kyushu, a clan leader who went by the name of Iwai and who was governor of Tsukushi Province had rebeled against orders to provide troops and supplies for an expedition against Silla. According to the Nihon shoki, Iwai had accepted bribes from Silla and obstructed the mobilization of troops. The Yamato court’s military plans had been thwarted and forces had to be diverted to put down the Iwai rebellion and have Iwai killed.
Royal estates are established in outlying provinces
Following the Iwai rebellion, the Yamato court then took steps to strengthen its control in the land. Strong clans like Iwai’s were appearing in most regions, but especially on the Kanto plain and the Kibi plateau where agricultural land had been opened up, increasing the wealth and power of the clans in control of those lands. Immediately, after Iwai’s defeat, in 528 the Yamato court set up royal estates in Tsukushi (Iwai’s domain), and then in other distant provinces where the Yamato court had had to use military force either against an uncooperative provincial governor or in order to instal its own loyal appointed provincial governors (called Miyatsuko) to manage the royal estates.
Nihon shoki lists such royal estates established in more than a dozen provinces in the reign of Emperor Ankan in 535. The royal estates were usually established in outlying regions of special and economic and strategic value to the Yamato court. The Yamato court appointed its own provincial governors to manage these royal estates.