Koshu Mirror
This square bronze mirror was made in Huzhou, China during the Southern Sung period (1127–1279). It is known as a Koshu (Huzhou) mirror due to the Chinese inscription on the back, which includes Chinese characters that read Koshu-shin (Huzhou).
The mirror was unearthed during the excavation of a pit dwelling next to the Kushiro River, close to the Nusamai Bridge in downtown Kushiro. There was a village in this area during the Satsumon period (600–1200). The people lived in pit dwellings, which consisted of an earthen pit about a meter deep, covered by a thatched roof supported on wooden poles.
Similar mirrors of various shapes have been found along the coast of the Sea of Japan, from the Kinki region of central Honshu to the Tohoku region in the north. However, this is the only square Koshu mirror that has been found in Hokkaido. It is believed to have come to Kushiro from China through trade with the Okhotsk people, who settled areas around the Sea of Okhotsk after the fifth century.