The kofun were excavated in 1692 by order of Tokugawa Mitsukuni, who kept a detailed illustrated records of the artifacts discovered.

The artifacts were later placed in boxes made from Japanese red pine restored to the burial chambers, and the site was backfilled.

Artifacts included bronze mirrors, fragments of armor, cylindrical beads and iron balls.

Artifacts included bronze mirrors, iron swords and Haji ware pottery.

In 1975, the Shimo-Samuraizuka was trench excavated in connection with a land improvement project and more Haji-ware shards were discovered.