[1] The Nakasu Higashibaru site developed around a port located in a low swamp behind the sand dunes on the left bank of the estuary of the Masuda River western Shimane Prefecture.

This dock was made by laying fist-sized to human-head-sized gravel on a gentle slope along the shoreline of a lagoon.

The Masuda clan occupied this area from the Kenkyū era (1190-1198) of the early Kamakura period, until shortly after the 1600 Battle of Sekigahara.

Surviving documents of the Masuda clan includes numerous mentions of maritime trade, and several references to the Nakasu port.

In 1568, the Masuda clan is recorded as having presented the Mōri clan with several Siberian tiger pelts from Korea, and a large amount of contemporary Korean ceramics has been found at the Nakasu site.