Kawayu Onsen (Hokkaido) — relief & relaxation | Compare & book inns

Overview

Kawayu Onsen is a hot spring resort in eastern Hokkaido, located within Akan-Mashu National Park. A river of hot spring water flows through the town center, creating a unique atmosphere with steam and the distinct scent of sulfur. The source is the active volcano Mt. Atosanupuri (Mt. Iō), allowing visitors to experience its raw geothermal power directly.

Discovered in the late Edo period, it has long been used as a therapeutic spa (tōji). Its most remarkable feature is its water quality, with a pH of around 2.0, making it one of Japan's most acidic springs. The town proudly upholds a "100% Gensen Kakenagashi Declaration," ensuring that all facilities offer pure, undiluted, and non-recirculated hot spring water.

Iconic Spring Types & Benefits

The water at Kawayu Onsen is so acidic it can dissolve an iron nail in a few days. This strong acidity is believed to have a powerful sterilizing effect, long-cherished by those with skin conditions. Rich in sulfur, the water provides a distinct tightening sensation on the skin upon bathing.

• Atopic dermatitisThe strong acidity of the water provides a powerful sterilizing effect. This may help alleviate symptoms by acting on bacteria on the skin surface that can aggravate the condition.
• Psoriasis vulgarisAs with other chronic skin conditions, the spring's highly acidic and sterilizing properties are considered beneficial. This quality is a general indication for acidic springs in Japan.
• Chronic eczema
• Diabetes
• Peripheral circulatory disorders

Water Characteristics & Best Season

As the source temperature is high, many facilities use heat exchangers or traditional "yumomi" (water stirring with large paddles) to cool the water for bathing. The water is clear but may turn cloudy white when exposed to air. Winter is when Kawayu Onsen's magic truly shines. From December to March, you can witness fantastical phenomena like "muhyō" (rime ice) and "diamond dust." The limited-time, giant open-air bath "Sennin-buro" is another winter highlight.

Access

Nearby Attractions & Local Cuisine

• Mt. Iō (Atosanupuri): Experience the power of a volcano up close with its rising steam vents.
• Lake Mashu: A caldera lake known for its mists and world-class water clarity.
• Lake Kussharo: Japan's largest caldera lake, featuring "Sunayu," where hot spring water bubbles up when you dig into the sand on its shore.
• Kawayu Eco-Museum Center: Learn about the region's nature and culture.
• Teshikaga Ramen: A local ramen featuring a double soup of seafood and pork bone broth.
• Mashu Soba: Flavorful buckwheat noodles made with the pure subsoil water of Lake Mashu.
• Local Dairy Products: Enjoy soft-serve ice cream and cheese from cows raised on vast pastures.