The Kaidahara mounded tomb No. 20 is the largest burial in the Kaidahara mounded tomb group. It became clear, that the burial mound is scallop shell-shaped (hotategaigata kofun) and is about 36 meters in length and five meters high. A report on the artefacts collected from this site is presented in this study, The finds are all kept in the Kisa Museum of History and Folklore. They include Sue ware and cylindrical ceramic clay figures (entō haniwa). The Sue ware mostly consists of pots with bellied body (kame), kinds of jars (tsubo), but also dishes (tsuki), dishes with pedestal (takatsuki), vessels with a funnel-shaped wide mouth and a small hole in the spherical body (hasō), handles and vessel stands etc.
Previously, due to the characteristic mound shape type the construction date was placed in the middle of the 5th century AD. But one of the results of this study is, that the associated Sue ware is more consistent with a construction during the second half of the 6th century AD. Kaidahara mounded tomb No. 20 is an important example of a large scallop shell-shaped mounded tomb which was built during the Late Kofun Period.