When it comes to Japanese hot spring culture, few destinations are as iconic or as historically rich as Kusatsu Onsen (草津温泉). Nestled in the mountains of Gunma Prefecture, Kusatsu has drawn visitors for over a millennium, offering not only therapeutic waters but also a profound connection to Japan’s spiritual, cultural, and natural heritage.
The Origins of Kusatsu Onsen: Legend Meets History
The history of Kusatsu Onsen stretches back to at least the Heian period (794–1185). According to legend, the hot springs were discovered in 804 AD by Sakanoue no Tamuramaro, a legendary military commander, though natural records suggest that local communities likely knew of the springs even earlier.
- During the Edo period (1603–1868), Kusatsu became one of Japan’s most celebrated therapeutic resorts.
- Samurai, aristocrats, and later literary and artistic figures frequented Kusatsu for its powerful healing properties.
- Historical documents record shoguns and feudal lords sending their retainers to Kusatsu for treatment.
The name “Kusatsu” may originate from the phrase “kusahaetsu” (草生津), meaning grass-growing port, referring to the abundant spring waters nourishing lush greenery around the Yubatake (湯畑) — Kusatsu’s iconic hot water field.
The Unique Chemistry of Kusatsu’s Waters
What sets Kusatsu apart from other hot springs across Japan is its uniquely potent mineral composition:
- Type: Acidic sulfate spring (“Kusatsu-type” spring)
- pH level: Approximately 2.1, making it one of Japan’s most acidic hot springs.
- Temperature: Springs can reach up to 50–60°C (122–140°F).
Thanks to this strong acidity, Kusatsu’s waters are believed to offer a wide range of health benefits:
- Treatment for chronic skin conditions (eczema, psoriasis, atopic dermatitis)
- Relief from muscle pain, neuralgia, and joint stiffness
- Improvement of digestive disorders and gout
- Regulation of high blood pressure and diabetes
- Therapeutic support for certain gynecological disorders
However, the same acidity that offers these therapeutic effects requires caution — bathers are encouraged to limit soak times to avoid skin irritation.
Yubatake: The Heart of Kusatsu Onsen
The beating heart of Kusatsu is the Yubatake (湯畑, “hot water field”), where steaming spring water gushes up from the earth before cascading through wooden chutes to cool and aerate:
- The Yubatake produces an estimated 4,000 liters (over 1,000 gallons) of hot spring water every minute, making it one of Japan’s most productive hot springs.
- The striking wooden structures surrounding the Yubatake serve both aesthetic and practical purposes, helping to regulate water temperature before it reaches local baths.
The area around Yubatake forms Kusatsu’s bustling town center, lined with traditional ryokan inns, souvenir shops, footbaths, and atmospheric lantern-lit streets.
Yumomi: A Living Tradition
One of Kusatsu’s most cherished and unique cultural traditions is the Yumomi (湯もみ) ceremony — a ritual cooling of the hot spring water:
- Performers in traditional attire use large wooden paddles to stir and cool the steaming water.
- The process lowers the temperature without diluting the mineral-rich waters, preserving their therapeutic properties.
- Yumomi is often accompanied by folk songs, rhythmic clapping, and lively performances, offering visitors a glimpse into Kusatsu’s living cultural heritage.
Today, visitors can watch or even participate in Yumomi demonstrations at Netsunoyu (熱乃湯), located near the Yubatake.
Beyond the Baths: Exploring Kusatsu’s Natural and Cultural Beauty
While the hot springs are the main attraction, Kusatsu Onsen offers much more to explore:
Sainokawara Park (西の河原公園)
- A serene natural park along the Kusatsu River.
- Features open-air hot spring pools surrounded by seasonal landscapes, especially stunning in autumn and winter snow.
Kusatsu Tropical Botanical Garden
- A greenhouse complex heated by geothermal energy.
- Showcases exotic tropical plants and wildlife unusual for this mountainous region.
Shirane Volcano (Mt. Kusatsu-Shirane)
- The nearby volcanic mountain provides scenic hiking trails and panoramic views.
- The region’s volcanic activity fuels the very springs that make Kusatsu famous.
Kusatsu Onsen in Modern Japan: UNESCO and Global Recognition
Kusatsu is not only one of Japan’s top three traditional hot springs (alongside Arima Onsen and Gero Onsen) but has also garnered increasing international attention:
- Frequently ranked as Japan’s most popular hot spring destination.
- Recognized for its efforts to preserve centuries-old bathing customs while welcoming global visitors.
- Part of Japan’s broader intangible cultural heritage of bathing and wellness.
Summary
Kusatsu Onsen is far more than a hot spring resort — it’s a living embodiment of Japan’s harmony between nature, healing, and tradition. From its legendary origins and powerful acidic waters to the unique Yumomi ceremony and stunning mountain scenery, Kusatsu offers visitors an immersive journey into Japan’s timeless onsen culture.
Whether seeking physical healing or simply a moment of peaceful reflection, a visit to Kusatsu Onsen promises rejuvenation for both body and soul — a tradition still as potent today as it was over 1,000 years ago.
