The Masuda Plain in the 13-16C had a natural port as a sandbank made a lagoon at the mouth of Masuda River.

The Nakazu Higashihara Ruins Site was located at the estuary at the time.
There was a sand dune in the north of the ruins and in the south there was a landing place covered with gravels.
A building structure with earth-fast posts, a forge and roads were also found here.

The port started to develop from 12C and its peak was 14 – 16C.
Ceramics made in China, Japan, Korea and Thai were found.
Ancient documents such as “Masudake Monjo”(Masuda clan archives) shows the Masuda clan were deeply involved in the trades.

It is a significant ruin to study how a port town was made and developed or how people traded in the 12-16C.