Kamuiwakka Falls (“Kamuiwakka Yunotaki”) is a unique hot-spring waterfall on the Shiretoko Peninsula in Shari Town, Shari District, Hokkaidō—a UNESCO World Natural Heritage site. Its name comes from the Ainu words for “god’s water.” Acidic spring water emerging from the slopes of nearby Mount Iō (Sulphur Mountain) flows into the river, creating a warm cascade you can actually climb.

As you wade upstream, the water gradually warms, offering a one-of-a-kind experience part way between bathing and “shower-climbing.” Surrounded by primeval forest, you’re immersed in raw nature—and since 2023 it’s been operated exclusively via guided tours, with park rangers on hand. Bathing is mixed-gender, and you must follow your guide’s instructions at all times.