Sunayu on the eastern shore of Lake Kussharo offers a unique open-air hot spring experience. If you dig a hole in the sandy beach, natural hot spring water gushes to the surface to create a warm pool. Visitors can soak their feet in the water while taking in the beautiful view of the lake.

The area around Sunayu can be enjoyed year-round. In summer, visitors flock to the shore to swim in the lake and go camping, while in winter, a whooper swan colony comes to Lake Kussharo from Siberia, attracted by the geothermal activity. Sunayu is a popular spot for photographers to capture shots of whooper swans against backdrops of fresh snow and frozen water. There are shops, toilets, and a campground nearby.