Kumanoyu (Bear's Hot Spring) is a free, open-air natural hot spring located in the town of Rausu on the Shiretoko Peninsula, a UNESCO World Heritage Site in eastern Hokkaido. This historic onsen has been in use since the Meiji era, originally serving as a place for local fishermen to rest after long days at sea. The name derives from frequent bear sightings in the area. The spring water is classified as a sulfur-containing sodium chloride hot spring (hydrogen sulfide type), with a neutral pH of 7.3 and a source temperature of 77.4 degrees Celsius. The milky-white water carries a distinctive sulfurous aroma and is beneficial for neuralgia, muscle pain, skin conditions, and fatigue recovery. The bathing temperature ranges from 45 to 50 degrees Celsius, which is considerably hot. The facility features separate outdoor baths for men and women with simple changing areas. It is managed by a local volunteer group called the Kumanoyu Aikokai, who enforce strict bathing etiquette known as the Ten Commandments of Kumanoyu. Swimwear is not permitted. Open 24 hours except during early morning cleaning around 5:00-7:00 AM.