The Komagata Ōtsuka Kofun within this cluster received protection as a National Historic Site in 1979, and the other groups were added in 2002.

The sites are located about 1 hour and 30 minutes by car from JR Tōhoku Shinkansen Utsunomiya Station.The cluster consists of the following: This keyhole-shaped kofun has a total length of 64 meters.

The tumulus was excavated in 1974, and was found to contain a burial chamber with a wooden casket with length of 3.2 meters and width of 75 centimeters.

Many grave goods were recovered, including earthenware, bronze mirrors, two knives, an iron ax, sword, as well as copper and glass ornaments.

The foundations of a pit dwelling measuring eight meters in diameter, with an altar-like step about 25 cm in height on the east side wall, was found, indicating that this was a ceremonial structure.

In an excavation conducted in 1952, the burial chamber with a split bamboo-shaped wooden casket with clay blocks on both ends in the east and west was confirmed one meter below the summit of the rear portion.