Length 104km, the Saru River, which is Hidaka's number one long river, takes the Hidaka Mountains as its source, and reflecting the charm of each season, is a beautiful river that flows leisurely. Even within the Ainu legends "Kamuy Yukar", numerous legends are told, and feelings towards the river that has nurtured life are conveyed. From the fact that water volume is abundant, dam development and other effective utilization plans are also progressing, the symbol of Biratori Town, the Saru River. As for its downstream, it is an attractive river that is also known as a mecca for Akahara fishing, etc.