The Otsuka Mausoleum Reference Site, noted for its many mirrors. Official sources differ on its length and construction date. Koryo Town regards it as the first large mound built in the Umami group.
Finds & research
The traditional assemblage includes 34 bronze mirrors, including triangular-rimmed deity-and-beast mirrors and straight-and-curved-pattern mirrors, beads, kuwagata stones, wheel stones, stone bracelets, gilt-bronze belt fittings, pedestal-shaped stone objects, and other items. The IHA study questions the provenance of some objects.
Official status & archaeological view
Official status
The Imperial Household Agency manages it as the Otsuka Mausoleum Reference Site.
Attribution (jitei): the Imperial Household Agency's determination of whose tomb it manages — separate from heritage designation.
Archaeological view
A square-fronted, square-backed mound at Otsuka, Koryo, on the southeastern edge of the Umami hills. Koryo Town gives a length of about 126m, while an IHA study gives about 137m. The town’s cultural resources guide dates it to the late 4th century, whereas its study of the Suyama area places it in the middle of the Early Kofun period. A pit-style stone chamber at the center of the rear mound reportedly yielded 34 bronze mirrors, beads, bracelet-shaped stone objects, gilt-bronze belt fittings, and other goods. The occupant has not been identified, and a government written answer on imperial mausoleums lists the occupant as unknown.
Field notes
It is managed by the Imperial Household Agency as the Otsuka Mausoleum Reference Site.