Horoshin Onsen (ほろしん温泉)

Introduction: The Luminous Forest Sanctuary of the Firefly Valley

Deep within the mountainous interior of Numata Town, where the air is pure and the water runs crystal clear, lies Horoshin Onsen (ほろしん温泉). This hot spring is a centerpiece of “Hotaru-no-Sato” (Home of the Fireflies), a region dedicated to the preservation of Japan’s most magical nocturnal insects. For the international traveler, Horoshin Onsen offers a profound encounter with the “Quiet North.” It is a place where you can soak in mineral-rich waters while surrounded by dense birch forests, witness the ethereal glow of thousands of fireflies in mid-summer, and explore the rugged history of Hokkaido’s coal mining pioneers. Whether you are seeking a romantic summer evening of natural light displays or a quiet winter retreat buried in several meters of snow, the warm, restorative embrace of Horoshin Onsen provides an authentic escape into the Japanese wilderness.

Key Information Table

The Healing Waters: The “Silk Water” of the Firefly Forest

The water at Horoshin Onsen is a high-quality Simple Sulfur / Sodium-Chloride Spring. It emerges from the ground with a soft, translucent appearance and a very subtle, pleasant mineral aroma.
The Skin Effect: The mildly alkaline nature of the water acts as a natural cleanser, gently emulsifying skin oils and leaving your body feeling exceptionally smooth—a sensation described by locals as “silk-on-skin.”
Thermal Retention: The chloride content ensures that your body core stays intensely warm for hours after your soak. The facility, Hotaru-kan, features a spacious indoor bath with panoramic windows looking out into the forest, and a beautiful outdoor Rotenburo where the only sound is the rushing of the nearby Horoshin River. In winter, the steam creates a private cocoon that allows you to enjoy the frigid air in complete comfort.

Top Recommended Stay: Horoshin Onsen Hotaru-kan

• Horoshin Onsen Hotaru-kan (ほろしん温泉 ほたる館): The central hub for wellness and lodging. This hotel is designed to look like a historic manor, offering spacious Japanese and Western rooms. The dining hall is a major attraction, serving “Numata Beef” and “Numata Rice” (Nanatsuboshi). It is the absolute best place to stay during the July firefly season, as the viewing area is just steps from the hotel lobby.
• Hotaru-no-Sato Campground: Located adjacent to the onsen, this is one of the top-rated campsites in Hokkaido. It offers high-quality bungalows and turf sites. Many international “Van-life” travelers use this as a base for exploring the central interior.

Must-Visit Neighborhood Spots: Fireflies and Steam Trains

Hotaru-no-Sato (Firefly Viewing Area): From early July to early August, this is one of the best places in Japan to see Heike-botaru and Genji-botaru fireflies. The sight of thousands of dancing lights along the river is a spiritual experience.
Showa Coal Mine Ruins: A 15-minute drive inland takes you to the eerie and fascinating remains of a former coal-mining city. The crumbling concrete structures and overgrown tracks are a favorite for photographers capturing “Haikyo” (modern ruins).
Numata Town Museum: Located in the town center, showcasing the history of the “Kurai Matsuri” (Numata Fire Festival) and the town’s pioneering heritage.

Local Gastronomy: The Bounty of the Numata Basin

Numata’s food is defined by its pristine mountain water and rich volcanic soil.
Numata Rice: Consistently ranked as “Special A,” the rice here is incredibly sweet. Try the rice balls (Onigiri) sold at the roadside station.
Numata Beef: A rare local wagyu known for its lean flavor and tenderness.
Vegetarian/Vegan Survival: Numata is a major producer of Soybeans and Buckwheat.
For Vegans: Try the local Handmade Soba. Order “Mori Soba” (cold noodles) and specify “Shio” (salt) or wasabi to avoid the fish dashi. The local “Numata Tofu” is also highly recommended for its creamy texture. In summer, fresh local corn and tomatoes are available at the Michi-no-Eki which are perfect 100% vegan snacks.

Cultural & Historical Context

The name “Horoshin” comes from the Ainu word “Poro-shin-nay”, meaning “big, calm river.” Historically, Numata was a booming coal-mining center. When the mines closed in the 1960s, the town reinvented itself as a sanctuary for fireflies, which had disappeared due to industrial pollution. The restoration of the firefly habitat is a proud achievement for the community. The onsen was developed as a symbol of this rebirth, providing health and recovery for the residents while welcoming the world to witness their environmental success.

Practical Travel Tips for International Visitors

• Tattoo Policy: Hotaru-kan is a community-focused facility and is generally tolerant of international travelers. Small tattoos are fine; for large pieces, using a waterproof sticker is recommended. There are no private baths, so visiting during the early afternoon (1:00 PM – 3:00 PM) when it is least crowded is a good strategy.
• Language Support: Basic English signs for the bath rules are provided. During the Firefly Festival, the staff are very welcoming to foreigners. Have a translation app ready for the dinner menu.
• Cash & Payments: The hotel accepts major credit cards. However, the day-trip bath ticket machine and the local festival stalls are cash-only (JPY).
• Transport: A rental car is highly recommended. While a bus from JR Numata Station exists, it is infrequent. The drive from Asahikawa via Route 233 is scenic and easy.

2025-2026 Latest Updates

In 2025, Horoshin Onsen launched a “Firefly Night Photography Tour,” providing specialized lighting and tripod zones for guests. For the 2026 season, a new “Eco-Sauna” using wood-waste from the local forests is being installed at the campground area, offering a hybrid thermal experience.

Safety & Manners

In the onsen, always sit on the provided stools while washing and do not splash water. Because the facility is in a mountain valley, be “Bear Aware”—carry a bear bell if walking the coal mine ruins. When viewing fireflies, never use flash photography or shine flashlights at the insects, as this disrupts their mating patterns and kills them. Respect the quiet of the forest; many guests come here specifically for the silence.