[1] The Ōzan Kofun Cluster is located on an isolated hill with an elevation of 62 meters near the centre of the modern city of Sabae, and consists of 49 tumuli dating to the late Yayoi period through the early Kofun period.

The borders of the area were revised and the new boundaries became a National Historic Site in 1967[2] A total of eleven tumuli were excavated in 1965 (No.

All of the tombs had grave goods, mostly pottery fragments, with the exception of No.1, which was completely bare.

5, 7, 9 and 25 were also square tombs, eight to fourteen meters on a side, but were dated from the early Kofun period, as indicated by the presence of fragments of swords and other weapons, and metal horse fittings found inside.

It is one of many similar tumuli which have been discovered in the area, which has been densely populated since the Yayoi and Kofun periods, and from its scale it must have been the tomb of a local chieftain or other person of importance.