Ikenoyu Onsen (池の湯温泉)

Introduction: The Giant Wild Basin of the Kussharo Shore

On the southeastern edge of Lake Kussharo, where the geothermal heat of the earth meets the icy waters of the caldera, lies Ikenoyu Onsen (池の湯温泉). This is not a “town” or a “resort,” but one of Hokkaido’s most iconic and primitive “wild” hot springs. Known for its massive, circular outdoor bath that feels like a natural pond (hence the name “Ikenoyu” or “Pond Bath”), it is a destination for the true adventurer. Surrounded by tall reeds and the vast horizon of the lake, Ikenoyu offers a raw, unfiltered encounter with nature. For the international traveler, Ikenoyu Onsen provides a rare sensory experience: soaking in mineral-rich “Moor-style” waters while watching whooper swans glide just meters away during the winter months. It is a place of absolute freedom, rugged beauty, and a thermal intensity that captures the wild, unpolished heart of eastern Hokkaido.

Key Information Table

The Healing Waters: The “Algae-Rich” Organic Bloom

The water at Ikenoyu Onsen is a unique Simple Bicarbonate Spring. Unlike the clear volcanic springs elsewhere, the water here has a distinct greenish-amber tint. This is due to the presence of “Onsen-algae” and organic minerals that thrive in the gentle temperature of the pond. For some, the sight of green algae can be surprising, but it is a sign of a healthy, natural ecosystem. The water is incredibly slippery and moisturizing, acting like a natural body oil. The temperature is usually around 40-42°C, but it can fluctuate depending on the season and the amount of lake water mixing in. The sensation of soaking in such a large, open space while being enveloped in the scent of reeds and lake mist is one of the most therapeutic experiences in the national park.

Top Recommended Bases & Logistics

Since you cannot stay at Ikenoyu, travelers use the surrounding areas as their base camp.

• Kotan Onsen Area (5 mins away): Several small, charming guest houses like “Guesthouse Kotan” offer affordable stays and easy access to both Ikenoyu and the famous Kotan lakeside bath.
• Teshikaga Town Hotels: A 15-minute drive takes you to the town center, which offers modern business hotels and a wide variety of restaurants.
• Lake Kussharo Campground: Located at the nearby Wagoto Peninsula, this is one of Japan’s best campgrounds. Many “Van-life” travelers camp here and drive to Ikenoyu for their morning soak.

Must-Visit Neighborhood Spots: Reeds and Swans

Kotan Onsen: Another wild bath located just 2km away. It is better known and has better-maintained changing rooms, making it a good “first step” before visiting the more primitive Ikenoyu.
Wagoto Peninsula Trail: A beautiful hiking trail that circles the peninsula, featuring volcanic vents and spectacular views of the lake’s central island.
Kaminoko-ike (nearby district): While an hour away, many visitors combine a trip to Ikenoyu with a visit to the “Blue Pond” of eastern Hokkaido.

Local Gastronomy for Adventurers

There are no shops at Ikenoyu, so you must bring your own supplies.
Wakasagi Ramen: Head to the small restaurants in the Sunayu or Wagoto areas to try ramen topped with lake smelt.
Vegetarian/Vegan Survival:
For Vegans: Teshikaga is famous for its “Mashu Buckwheat” (Soba). In the town center, you can find excellent Soba shops. Specify “Shio” (salt) or “Soy sauce only” to avoid the fish-based dashi. The local “Michi-no-Eki” sells fresh local corn and roasted potatoes in summer which are perfect 100% vegan snacks. Important: Take all your food trash back with you to protect the wildlife.

Cultural & Historical Context

The name “Ikenoyu” literally means “Pond Hot Spring.” For generations, this massive pool was used by local farmers and their families as a social gathering spot and a place to wash after a day of work. It is maintained by a dedicated group of local volunteers who clean the tub and manage the simple changing rooms. It remains a symbol of the “Communal Bathing” culture of rural Japan, where the lack of luxury is replaced by a deep sense of belonging to the landscape.

Practical Travel Tips for International Visitors

• Tattoo Policy: As a wild, outdoor spot with no staff, there are no restrictions on tattoos. It is a haven for international travelers with ink.
• Bathing Style: Ikenoyu is a mixed-gender bath (Konyoku). While many locals bathe naked, wearing swimwear is permitted and common among international guests and female travelers here. There is a simple wooden changing partition for men and women.
• Algae Note: The tub floor can be very slippery due to the natural algae. Walk carefully. You may also see small water insects; they are harmless and part of the natural thermal environment.
• Cash Only: While there is no fee, there is often a small donation box to help the volunteers with cleaning supplies. Bring a few 100-yen coins.

2025-2026 Latest Updates

In 2025, the local volunteer group improved the wooden boardwalk leading from the parking area to the bath to make it safer during the snowy months. For the 2026 winter season, a new “Swan Awareness Program” is being launched, providing English brochures at the nearby rest area explaining how to enjoy the onsen without disturbing the migratory birds.

Safety & Manners

In the onsen, do not use soap or shampoo—the runoff goes directly into Lake Kussharo. Keep the water pure. If you are visiting in winter, be aware that the area around the bath can be icy and extremely slippery. Be “Bear Aware”—while rare near the shore, the forest behind the onsen is bear territory; keep your food sealed. Finally, respect the “Silent Hour”—early morning and sunset are peak times for photographers and wildlife; avoid loud conversation during these times to enjoy the majesty of the lake.