Lake Kussharo Onsen-kyo: Geothermal Wonders Around the World’s Largest Caldera Lake
Lake Kussharo Onsen-kyo is a collection of diverse thermal springs scattered along the shores of Lake Kussharo, Japan’s largest caldera lake and the sixth-largest lake in the country. This region is a playground for geothermal activity, where the earth’s internal heat manifests in unique ways—from “Sunayu,” where you can dig your own hot spring bath in the sand, to the lakeside “Kotan Onsen” where you can soak just inches away from migratory whooper swans. Located within the Akan-Mashu National Park, the area offers an incredible sense of scale and a raw connection to Hokkaido’s volcanic origins. For the international traveler, Kussharo provides a blend of outdoor adventure and peaceful immersion, where the steam of the springs meets the crystal-clear waters of the caldera, creating a year-round sanctuary of light and heat.
Key Information
| Address | 〒088-3331 北海道川上郡弟子屈町 / Teshikaga Town, Kawakami District, Hokkaido |
| Google Maps | View on Google Maps |
| Spring Quality | Sodium-Bicarbonate, Chloride, and Simple Hot Springs (Varies by site) |
| Benefits | Neuralgia, fatigue recovery, chronic skin conditions, joint stiffness, and moisturizing effects |
| Access | 20 min by car from JR Mashu Station; 70 min by car from Memanbetsu Airport |
| Number of Ryokans | Approximately 10-15 properties including grand resort hotels, rustic lodges, and lakeside pensions |
| Day-trip Bathing | Available at Sunayu, Kotan Onsen (free), and major facilities like the Kussharo Prince Hotel |
The Healing Waters: Caldera Magma and the “Bicarbonate Silk” Science
The waters of Lake Kussharo are fed by the volcanic activity of the Kussharo Caldera, which formed roughly 30,000 years ago. Scientifically, the springs in this area are primarily sodium bicarbonate saline waters. These are often referred to as “Beauty Baths” because the bicarbonate ions act as a natural soap, gently emulsifying skin oils and removing old keratin to leave the body feeling silky and smooth. The chloride content in some sources, such as Wakoto and Nibushi, creates a mineral film on the skin that prevents heat from escaping, making these baths exceptionally effective for warming the body’s core during the frigid sub-zero winters. Because the water volume is so high, many lakeside baths use a “Gensen Kakenagashi” (100% natural flow) system, allowing for the direct transdermal absorption of minerals in their most bioactive state.
Top 5 Recommended Ryokans & Stays
- Kussharo Prince Hotel (Resort/Scale): A flagship resort located right on the lakeshore. It features a grand open-air bath surrounded by a forest of white birch and spruce, offering full Western-style amenities and expansive buffet dining.
- Lake Kussharo Tsuruga Auberge SoRa (Luxury/Gourmet): A refined, small-scale lodge focused on high-end French cuisine made with local Teshikaga ingredients. It offers a sophisticated retreat with a private onsen atmosphere.
- Nibushi no Sato (Authentic/View): A historic lakeside inn known for its cozy wooden baths and its proximity to the whooper swan gathering points. It provides a traditional “At-home” Japanese hospitality experience.
- Kussharo Genya Youth Guesthouse (Budget/Solo): A high-quality budget option popular with international hikers and canoeists, known for its friendly owners and deep knowledge of the park’s secret spots.
Must-Visit Public Baths (Soto-yu)
Kussharo is world-famous for its free, wild “Soto-yu” experiences. Sunayu (Sand Bath) is a unique spot where geothermal heat warms the beach; in winter, you can see swans basking in the warm sand, and in summer, you can dig your own individual bath in the shore. Kotan Onsen is arguably the most beautiful mixed-gender open-air bath in Hokkaido, separated from the lake by only a few stones. For those seeking privacy, Wakoto Onsen features a small stone-lined pool on the peninsula that is beloved by locals for its intense mineral clarity. All these wild baths are free of charge, but visitors should bring their own towels and respect the local manners.
Walking Guide & Scenic Spots
Start with the Bihoro Pass Observatory for a breathtaking panoramic view of the entire 26-kilometer caldera and the central island (Nakajima). Next, walk the Wakoto Peninsula Nature Trail, a 2.5-kilometer circuit through primary forest where you can see rare mosses and active steam vents near the shore. For birdwatchers, the **Kussharo Lakeside Path** near Nibushi is essential in winter to see the hundreds of whooper swans that gather in the non-freezing geothermal pockets of the lake. For active adventurers, the Kushiro River Headwaters Canoe Tour starts at the lake’s outlet and offers a peaceful float through a pristine “Gallery of Water and Trees.”
Local Gastronomy & Souvenirs
The culinary highlight of Teshikaga is **Mashu Pork**, often served as “Butadon” (pork bowl) in local ryokans. The lake is also home to **Himemasu (Kokanee Salmon)**, a delicacy best enjoyed as sashimi or grilled with salt. For a trendy break, visit Mashu Yaki Pottery to see ceramics glazed with the unique minerals of the region. Souvenirs to look for at the Michi-no-Eki Mashu Onsen include “Marimo” (moss ball) themed goods, local honey from the forest blossoms, and the famous **Mashu Melon**, which is exceptionally sweet due to the mountain air.
Cultural & Historical Context
The name “Kussharo” comes from the Ainu word kucchar, meaning “the place where the lake becomes a river.” Historically, the Ainu utilized these shores for seasonal fishing and used the thermal sands for purification. The area gained national fame in the 1970s due to the legend of Kusshie, a rumored giant lake monster similar to Nessie. Today, the town is a leader in Eco-Tourism, focused on preserving the crystal-clear water quality of the caldera while providing a gateway for international travelers to experience the “Primitive North.”
Practical Travel Tips
Transportation: A car is essential for exploring the various lakeside springs efficiently. For winter travelers, a special Winter Bus service is scheduled to run from January 24 to March 1, 2026, connecting Mashu Station to the western shores. Wildlife: Whooper swans are common in winter; please do not feed them or disturb their habitat with drones. Mixed Bathing: Kotan Onsen is a mixed-gender bath (Konyoku) where swimsuits are allowed during the day. Cash: Small lakeside cafes and souvenir stands are strictly “Cash Only”; ensure you have enough Japanese Yen on hand.
2025-2026 Latest Updates
In early 2026, the new Hoshino Resorts KAI Teshikaga project in the nearby Kawayu area will be progressing, bringing increased high-end tourism attention to the Kussharo basin. Additionally, the Lake Kussharo Night Starlight Tour has been updated for the 2025-2026 winter season, offering professional-led photography sessions for visitors seeking to capture the “Ice Bubbles” and the Milky Way over the caldera.
Safety & Manners
In the wild open-air baths, always maintain a quiet and respectful tone to preserve the tranquil atmosphere. When digging a sand bath at Sunayu, be careful as the water can sometimes exceed 60 degrees Celsius—always mix in lake water to reach a safe temperature. Please pack out all trash to protect the Akan-Mashu National Park ecosystem. Finally, in the traditional ryokans, ensure you follow the “Arai-ba” etiquette of washing thoroughly before entering the communal tubs.
