In the fifth century, the five kings of Wa (yamato, ancient Japan) dispatched envoys to China. Inscriptions on the 'Gwanggaeto Stele' (Gwanggaeto Stele was built in '411' by King Jangsu of Goguryeo Jian, Jinling Province, China) and other documents support these historical events. Japanese external relations in this historical period, the fourth century onward, included militaristic advances upon the Korean peninsula this resulted in the subjugation of the Silla (an ancient Korean Kingdom) and Paekche (an ancient Korean Kingdom), and furious battles with Goguryeo (an ancient Korean Kingdom). For royal tombs of 'okimi' (great king), specially octagonal tumulus were constructed. For a while afterwards, the construction of square tumulus and circular tumulus continued. Historians and other experts believe that the disappearance of the keyhole-shaped mounds, during this historical period, was dependant upon and directly related to the impact of 'Yamato sovereignty' gaining greater political power. After the establishment of the 'Yamato' sovereignty,' central and local political systems were established within Japan.

However, it was around end of the sixth century that keyhole-shaped mound building ceased in Japan. There were numerous gigantic 'Kofun' (keyhole-shaped mounds) continuously built throughout Japan during the mid fifth century. Finally, at the end of the fourth century, advanced tumulus communities appeared in one area of the Kinai region (the five capital provinces surrounding the ancient capitals of Nara and Kyoto). Furthermore, a gigantic 'Kofun' (tumulus) was built, taking nearly one century to construct on the Kawachi Plain by future generations of the regions subjects throughout the fourth century.

Then, from the middle to end of the fourth century, in a fifty year period, four large keyhole-shaped mounds of the 'okimi' (great king) class in scale of size were built in the Saki (also pronounced, 'Sofu') region of the Northern Nara Basin. In the latter half of the third century and onward large keyhole-shaped mounds which were considered to be imperial mounds, were significantly scaled up from the mounds in the early 'Kofun period' and appeared in Nara Basin. 'Historians and other experts considered that this 'Yamato sovereignty' provided to the powerful families or clans of Japan the permission to build the keyhole-shaped mounds it was through this mound permission process that a unified authority was established. 'Īt some point during the 'Kofun period,' 'Yamato sovereignty' (the ancient Japan sovereignty) was established as the unified authority of 'Yamato (ancient Japan). Taking into consideration what was known of the 'Kofun period' as a view point into the establishment of the Japanese Nation, historians and other experts came to this conclusion that ancient Japan was formed during the early and middle portions of the 'Kofun period,' then to be fully developed and established during the late and final periods of the 'Kofun. This period would occasionally be referred to as the final 'Kofun period. 'After the keyhole-shaped mounds were no longer built, mound construction would continue from the seventh century onward but with other forms of tumulus built shapes: the square tumulus, circular tumulus, and octagonal tumulus. However, especially during the period of the mid-third century to the late sixth century, these were the years of the 'Kofun period' in which the Japanese people built many keyhole-shaped mounds throughout the northern territory of the 'Tohoku Region' and the southern 'Kyushu region' therefore, this period would sometimes be referred to as the 'keyhole-shaped mounds period. In general, the 'Kofun period' (tumulus period) refers to the period ranging from the middle of the third century to the later part of the seventh century, approximately 400 years.

Kofun pottery happy farmer