Haniwa at the Saitobaru Museum
The “Book of Man (Hotsuma Tsutae)”, Chapter 38 relates the Yamato defeat of the Kumaso about 300 AD:
Prince Kousu and his entourage arrived in Tsukushi (ancient name of Kyushu) in the 12th month. There, they secretly spied on the movements of the Kumaso and studied the shape of the land.
One day, the Kumaso brave Toriishikaya (son of Sekaya) assembled his clan for a great feast by a river. When Kousu heard of this, he dressed himself in a young woman's garments, inside which he concealed a dagger. Then he went to mingle with a group of girls as they took a rest, and waited for his moment.
Soon Toriishikaya caught sight of the noble-looking girl dressed in her fine garments. He approached her and, taking her by the hand, led her into the inner room. He sat her on fancy matting, and amused himself with her as he drank.
The night wore on, and Toriishikaya let down his guard in his drunken state. Kousu now saw his moment. Taking the dagger out from inside his garment, he thrust it through his enemy's chest. It happened so quickly that Toriishikaya was powerless to resist. He could but raise a hand to stay Kousu's movement, saying:
"Hold your dagger, I beg you! I have something to say!" Kousu stayed his hand and let him speak. "Pray tell me who you are!", said Toriishikaya. "I am Kousu, son of the sovereign Woshirowake", replied the Prince.
"I am the strongest in this land. None may surpass me, and all obey me. There has been no man as valiant as you. For this, will you allow me to give you a name?" The Prince agreed. "From this day forth, may you be called Yamatotake, the Brave of Yamato." So saying, he breathed his last. Yamatotake then sent Otohiko and his men, who slew the remaining warriors and so completed the victory.
On the return voyage across the sea from Tsukushi, the Prince first landed at Kibi on the Anato Straits. There, he disposed of some violent brigands, before slaying a whole clan of miscreants in Kashiha, Namiha (today's Osaka).
On his return to the capital, he made this report to his father, "Guided by my sovereign's spirit, I was able to vanquish the Kumaso with my own might of arms. Since they are now all slain, there will surely be peace and wealth in the western lands henceforth. But in Anato of Kibi and the Kashiha Crossing of Namiha, there were still pirates who plundered the coastal lands and prevented people from crossing safely. Since these troublesome brigands were the root of these calamities, I easily overcame them, and have thus ensured the safety of sea and land."
Woshirowake was very glad to hear this. For the report by his son, who had returned to the capital after defeating the Kumaso, and had grown in stature by doing so, reminded him of his own past adventures in Tsukushi, where nothing could cause him any fear.
And he bestowed lavish gifts upon Kousu, now renamed Yamatotake, in recognition of his feat in pacifying the land.
From this time on Hyuga would never be the same. The Yamato invasion insured that Japanese language, culture, and civilization would be the dominant influence from 300 AD to the present. Quiet agrarian lifestyle would now include training for combat, building large burial mounds (kofun) for chiefs decorated with statues (haniwa), and paying taxes. This would later lead to periods of loyalty for the Emperor vacillating to periods of loyalty for Shogun and samurai.
This period in Hyuga is known for the introduction of steel weapons and armor. The Yamato had succeeded in building an empire from Honshu to Kyushu. This empire was protected by the requirement for all men to be trained and ready in defense of the area.
The Yamato introduced a bureaucratic system that set regional boundaries. Kyushu, then known as Tsukushi, was divided into the provinces Buzen, Hizen, Hyuga, Higo, Bungo, Osumi, and Satsuma. Yamato officials were responsible for primarily assuring taxes were collected and a proper force of men was raised to assure protection.
The main settlements in Hyuga were Takachiho, Nobeoka, Saito (including present day Sadowara, Miyazaki City, and Ikime), Aoshima, Nichinan, Ebino, Miyakonojo, and Toi. Kofun (burial mounds) are found in all these sites and none other.
A strict class system was in place. At the top were bureaucrats, local leaders close to the bureaucrats, artisans and teachers, merchants, warriors, farmers and trades people, and at the bottom slaves and beggars. No class could intermarry and rarely did one move up in class, although it was quite easy to move down. Any digression of Yamato law and ethics caused one to lose all class title and be handed over to the mercy of the bureaucrats who also acted as judges. Quite often they saw it as more expedient, and easy, to impose death rather than go through the trouble of stripping title and rank.
Agriculture was basically rice production throughout the Yamato Empire. It was more labor intensive, but produced more abundance than other crops. Wheat was still grown in Hyuga, but was a local staple. Only rice was accepted as currency and as payment for taxes. A barter economy also existed where merchants, artisans, and trades people exchanged goods and labor for other services and products. Teachers more often than not were supported for the performance of their duty by all in the community.
Eventually this system created a clan system that saw bureaucrats emerging as the chiefs of areas. Large tombs called kofun were erected for their burial. Personal items were placed in the kofun along, later, with weapons and armor made of iron. Terra cotta figures of animals and warriors called haniwa also decorated the burial chamber. Common people were buried in mass graves around the kofun of the chiefs.
The Yamato Empire eventually stretched into present day Korea. Great quantities of iron ore was sent to Japan and more advanced weaponry was introduced. Introduced also was Chinese writing and Buddhism. This alliance eventually broke down and great waves of Korean immigrants fled to Japan, most finding their way to Tsukushi.
The Yamato responded by sending court members to China to study Chinese government. By the early 7th century a Chinese style constitution was adopted. A very strict Confucian system emerged that put the Emperor at the top of society, followed by all government workers and military, teachers (including religious priests and monks), merchants and trades people, farmers, peasants, and at the bottom slaves.Hyuga found itself in the midst of a power struggle between local nobility and the Yamato Court, as did the rest of Japan. On one hand was loyalty to the local community and on the other loyalty to the Emperor. This identity crisis led the Yamato to tighten control and set a permanent capital in Nara. By 710 a firm Imperial system was in place and Nara was its capital. From 710 to 1179 the Emperor was the undisputed authority in Japan, and Hyuga as well.
Kofun Number 5 at Ikime Burial Mounds