Oji Forest-Sarufutsu, with an area of approximately 1,400 hectares, is a company-owned forest of Oji Paper, but is open to the public as a place for research, education, and cultural creation, with walking trails and other facilities maintained.

The marshland in this area is a marshland created by the landward expansion of the sea lakes and their surroundings, which were formed by the retreat of the sea after the Jomon Period, approximately 6,000 years ago.
It is a valuable marshland of high academic value, with the largest colony of mizugoke and red spruce wetland forests on the Sea of Okhotsk coast.