Kusatsu Onsen: Japan's Premier Hot Spring Town Guide

What Makes Kusatsu One of Japan's Top Onsen Towns

Kusatsu Onsen (草津温泉) consistently ranks among Japan's top hot spring destinations — it has held the number one spot in annual onsen surveys for years running. According to the Kusatsu Onsen official site, the resort produces approximately 32,000 liters of naturally flowing hot spring water per minute, one of the largest volumes of any onsen in Japan. That water arrives at the surface at over 90°C and is strongly acidic at pH 2.1.

The acidity is what sets Kusatsu apart. These sulfur-rich, acidic waters have been valued for centuries for their antibacterial properties and are traditionally associated with healing skin ailments. German physician Erwin Baelz, who studied Japanese hot springs in the late 1800s, called Kusatsu one of the finest hot spring sites in the world.

Kusatsu sits at approximately 1,200 meters elevation in northwestern Gunma Prefecture, giving it cool summers and snowy winters — both of which add to the bathing experience. This is one of the premier Gunma onsen town destinations and a cornerstone of any hot spring-focused trip to Japan. For details on how Kusatsu fits into the broader Gunma onsen landscape, see our guide to Kusatsu within Gunma Prefecture.

The Yubatake: Kusatsu's Steaming Heart

The yubatake (湯畑, literally "hot water field") is the center of Kusatsu — both geographically and atmospherically. This open-air hot spring source sits in the middle of town, where steaming water flows through rows of wooden flumes designed to cool it from over 90°C to a bathable temperature. The sulfurous steam rising from the yubatake is visible from blocks away, and the mineral smell reaches you before the sight does.

The yubatake is open 24 hours and free to visit. Surrounding it are free footbaths where you can test the waters — literally — before committing to a full soak. Many visitors on Reddit and travel forums recommend visiting the yubatake at night, when the steam is illuminated and the atmosphere shifts from tourist attraction to something more atmospheric.

The wooden flumes around the yubatake also serve a practical purpose: mineral deposits that collect on the wood are harvested and sold as yunohana (bath salts), a traditional Kusatsu souvenir. For a detailed walking guide around the yubatake and town center, see our Kusatsu town walking guide.

Public Baths and Where to Soak

Kusatsu's public bathing options range from large outdoor baths to small communal neighborhood facilities. No reservation is needed for any of them.

Sainokawara Park Outdoor Bath

Sainokawara Park (西の河原公園) houses one of Japan's largest outdoor hot spring baths — a spacious, rock-lined rotenburo set among trees and steaming streams. According to the official site, the bath is open from 6:00 to 20:00 (last entry 19:30). Admission is ¥600 (~$4) for adults and ¥300 (~$2) for children.

The setting is dramatic — natural rock pools surrounded by forested hillside, with steam rising from the water into the mountain air. In winter, snow collects on the rocks around the bath while you soak in the hot water, which is one of the defining experiences of a Kusatsu winter visit.

Communal Public Baths (Kyodo Yokujo)

Kusatsu maintains several kyodo yokujo (共同浴場) — small communal bathhouses scattered through the town. These are simple, no-frills facilities where you bathe in the source water alongside local residents. Shirane-no-yu (白根の湯), one of the accessible public baths, is open 8:00 to 16:00 and costs ¥300 (~$2) for adults, closed Tuesdays.

These communal baths are where you experience Kusatsu's waters at their most direct — the water is hot, strongly acidic, and undiluted. A few points worth noting:

• The pH 2.1 water can irritate sensitive skin. Test with a footbath first and limit your soak to 10-15 minutes on your first visit.
• Rinse thoroughly with fresh water after soaking — the acidity can cause dryness if left on the skin.
• Bring a small towel (required for onsen etiquette) and cash for admission.
• Communal baths are gender-separated with nude bathing. Check signage regarding tattoo policies — some facilities are becoming more accommodating.

Yumomi: The Traditional Water-Stirring Performance

Yumomi (湯もみ) is Kusatsu's signature cultural tradition — a performance where women in traditional dress stir steaming hot spring water with long wooden paddles, singing folk songs as they work. The practice dates back centuries, when the water needed to be cooled from its scalding 90°C+ source temperature without diluting the mineral content.

According to the official yumomi page, performances run daily at the Yumomi Hall near the yubatake. Shows are held at 9:30, 10:30, 13:30, 14:30, and 15:30, each lasting approximately 30 minutes. Admission is ¥800 (~$5.30) for adults and ¥400 (~$2.70) for children, which includes a small souvenir paddle.

The performers sing a well-known line: "All illnesses except lovesickness are cured here" — a saying that has been associated with Kusatsu for generations. Whether you take the medicinal claims seriously or not, the yumomi show is one of the few cultural performances at any onsen town that feels genuinely rooted in local history rather than staged for tourists.

Getting to Kusatsu from Tokyo

By Highway Bus from Shinjuku

The most common route from Tokyo is the JR highway bus from Shinjuku Expressway Bus Terminal directly to Kusatsu Onsen. The ride takes approximately 3.5 to 4 hours and costs around ¥4,000-5,000 (~$27-33) one way based on 2025 pricing. Buses run multiple times daily, but weekend and holiday departures sell out — book in advance through the JR Bus Kanto website.

The last bus from Kusatsu back to Tokyo departs around 17:00-18:00 depending on season. If you are attempting a day trip (not recommended — see FAQ), factor in the return timing carefully.

By Train via Naganohara-Kusatsuguchi

The train route goes from Tokyo or Ueno Station via the JR Joetsu Shinkansen to Takasaki, then the JR Agatsuma Line to Naganohara-Kusatsuguchi Station (長野原草津口駅). From there, a local bus reaches Kusatsu in about 30 minutes for ¥750 (~$5). The total journey takes roughly 2.5-3 hours and costs approximately ¥8,000+ (~$53+) — faster but more expensive than the highway bus.

If you hold a Japan Rail Pass, the Shinkansen and Agatsuma Line portions are covered, making this the more economical option for JR Pass holders. The bus from Naganohara-Kusatsuguchi is a separate fare.

Parking is available at town lots near the yubatake for ¥500-1,000 (~$3.30-6.70) per day for those driving.

When to Visit: Seasons and Considerations

Kusatsu is a year-round destination, but each season brings a different experience.

Season	Highlights	Notes
Winter (Dec-Mar)	Snow-covered yubatake, rotenburo in falling snow	Peak atmosphere for bathing; some baths may have reduced hours
Spring (Apr-May)	Mountain wildflowers, warming temps	Less crowded than winter; pleasant hiking weather
Summer (Jun-Aug)	Cool highland escape from Tokyo heat (1,200m elevation)	Green surroundings; hiking on nearby trails
Autumn (Sep-Nov)	Fall foliage around the town and hillsides	Popular period; book accommodation early

Winter is the most atmospheric time for hot spring bathing — the contrast of steaming water against snow is part of what makes Kusatsu iconic. But the 1,200-meter elevation means temperatures drop well below freezing, and heavy snow can occasionally affect bus schedules between November and March.

Summer offers a different appeal: the highland location keeps temperatures comfortable when Tokyo is sweltering, and the surrounding mountains provide hiking options. For travelers looking to combine Kusatsu with other Gunma hot springs like Manza Onsen, summer and autumn are the easiest seasons for road connections.