In Biratori Town, visitors can also get in contact with the lifestyles and cultures of the Ainu people (the indigenous people of Hokkaido) all over the town.
The Ainu people have many legends. One of them is the legend of Opushinupuri. A long time ago, the god Okikurumi, who lived at the Saru River, conducted a comparison of skills in order to avoid a conflict with another Ainu tribe that was attacking him. Legend has it that after shooting an arrow past the rugged mountain on the other side of the river, his enemy trembled in fear at his abilities and ran home. The dent made by that arrow still remains in the crest of Opushinupuri.
From mid to late June for a period of around ten days, there is a mystical moment that comes about wherein the falling sun fits right into the dent opened at Opushinupuri. Visitors can see it from an observation spot located next to Route 237.