(The Graduate University for Advanced Studies,
Sagami, Sannomiya Kofungun, keyhole-shaped tomb mounds, the relay station,
I propose an examination of the role of a local community in medieval Japanese society, from investigating aspects of Kofun and Yokoanabo (cave tombs) spread out in the Sagami region from the late 6th to 7th century.
It is known that there are some Kofun which have many possessions buried together with a dead body, such as the Tonoyama Kofun or the Rachimen Kofun in the Sannomiya area, Sagami region. This area was considered as a graveyard of the Sagami Kokuzo (国造) with respect to the abundance of possessions buried together with a dead body, characteristics of the horizontal stone chamber, and the dimensions of the tomb mounds. I call this area in which many Kofun and Yokoanabo are concentrated the “Sannomiya Kofun group” and I establish that the area encompasses 2.5 km square around Sannomiya-Hibita shrine, which was Shikinaisha (式内社) provided by Engishiki (延喜式) book of laws and regulations. And I interpret the Tonoyama kofun as a keyhole-shaped tomb mound through the observation of the present topography.
Recent excavations have revealed that there are many keyhole-shaped tomb mounds in the Sagami region. I compared the Sagami Kokuzo area, including the Sannomiya Kofun group, with the Shinaga Kokuzo area, focusing on the locations of tomb mounds and the structure of tomb types in a group. As a result, I found two phases. One is the case in which the main area of tombs were limited around a kofun group, and in the other case the main area of tombs moved along a river with the passage of time.
I also found abundant superior possessions buried with a dead body which were excavated from a tomb mound of the chief, in cases where there are tomb mounds and Yokoanabo in a same Kofun group area. With the passage of time, abundant superior possessions came to be buried with a dead body in Yokoanabo. In the case of the areas which are predominant in Yokoanabo, abundant superior possessions were buried in Yokoanabo the same as in a tomb mound of a chief. I think these areas acted as relay stations for the transportation of arms and other necessities for state control.
Many keyhole-shaped tomb mounds were made and then went out of use from the late 6th to the early 7th century, through the time of an interruption in making keyhole-shaped tomb mounds. I think these facts reflect that a keyhole-shaped tomb mound was made for one person for generations, as influenced by external factors rather than internal factors of the area. From the background of the political change in Asia and the political situation of the Korean Peninsula, the structure of Yamato Seiken (political power) confirms that local chiefs held Yamato Seiken, and local chiefs gained political power and support for local governments through keyhole-shaped tombs. This influenced the consensus of expectations of the central political power and local chiefs.