It is thought to have been built in the middle of the 6th century AD, based on haniwa excavated from the inner moat in 1968.

These included cylindrical, horse-shaped, equestrian statue-shaped, and shield-bearer shaped haniwa.

In an excavation of the main tumulus in 2018, it was found that the middle bank in the southwest corner protrudes partly to the outside.

Called a "Tsukuridashi", the shield-bearer shaped haniwa were also found lined up on the southwestern corner, indicating that this location was of some especial ritual significance.

There are very few examples of such Sue jars excavated in the Kantō region, and the fact that it was excavated from the second smallest burial mound towards the back of the cluster indicate that this tumulus had an importance greater than is reflected by its relatively small size.