Thematic GuidesFamous Japanese Hot Springs
Kusatsu Onsen Guide: Yubatake and Outer Baths
Explore Kusatsu Onsen in Gunma’s Kusatsu Town, from the steam-filled Yubatake scenery and highly acidic water around pH 2 to Netsunoyu, Sainokawara Rotenburo, outer-bath routes, access from Naganohara-Kusatsuguchi Station, and bathing tips.
Published: Jan 14, 2026
Thematic GuidesFamous Japanese Hot Springs
Kusatsu Onsen Guide: Yubatake and Outer Baths
Explore Kusatsu Onsen in Gunma’s Kusatsu Town, from the steam-filled Yubatake scenery and highly acidic water around pH 2 to Netsunoyu, Sainokawara Rotenburo, outer-bath routes, access from Naganohara-Kusatsuguchi Station, and bathing tips.
Published: Jan 14, 2026
Kusatsu Onsen is a hot spring resort in Kusatsu Town, Agatsuma District, Gunma Prefecture. It stands out for the iconic Yubatake at the center of the town and for its highly acidic water, around pH 2, one of Japan’s strongest. Located on a plateau at an elevation of around 1,200 meters, it is so rich in natural spring water that the volume is said to be the highest in Japan. Simply walking through town lets you feel the presence of hot springs through both sight and smell. It is an easy choice for a first famous onsen trip, but it is more enjoyable if you understand the water’s stimulation and the high temperature of the baths.
For travelers, the key is not just going because it is famous, but understanding the town layout centered on Yubatake and experiencing the highly acidic water without overdoing it. Kusatsu water is known for its strong disinfecting power, but it can irritate sensitive skin, and many baths are very hot. In this article, we organize the features and springs of Kusatsu Onsen, the best way to visit Yubatake, Netsunoyu, Sainokawara Rotenburo, and the outer baths, along with bathing precautions and access, based on official information from Kusatsu Town and the Kusatsu Onsen Tourism Association.
A hot spring town centered on Yubatake
Kusatsu’s symbol is Yubatake, located almost in the center of the onsen district. Water flowing up from underground runs through seven wooden channels, cools as it meets the air, and falls like a waterfall. At the bottom of the channels, yumohana deposits collect, and watching them being harvested is something unique to Kusatsu. The Yubatake source is said to gush at about 4,000 liters per minute, and its appearance changes dramatically between day and night, with steam and the shape of the wooden channels in daytime and illumination after dark.
Because the town is arranged radially around Yubatake, it is easy to explore on foot. Souvenir shops, restaurants, outer baths, and foot baths are gathered around Yubatake, so it is easiest to first walk a full loop around the area and get your bearings. The bus terminal is only a few minutes away on foot, making it a very convenient base for a stay.
The distinctive highly acidic water around pH 2
One essential part of Kusatsu’s story is its strong acidity. According to the official explanation from Kusatsu Town, the spring quality is acidic hypotonic high-temperature spring water, and the Yubatake source is said to have a very strong acidity of around pH 2.0. It is famously said that a nail left in the water of the stream will dissolve in about ten days, which places it among the most acidic waters in Japan. Highly acidic water is known for strong disinfecting power, but it also tends to be harsh on the skin.
In addition to Yubatake, Kusatsu has several other springs, including Yubatake, Bandai, Shirahata, Jizō, Nikawa, and Sainokawara. Among them, the Bandai source is said to have the largest output, and its temperature is also high. Since temperature, color, and perceived acidity differ by source, the bathing experience changes from one facility to another. If you want to know the spring quality for sure, the most reliable method is to check the spring analysis label posted at each facility.
Scientific details on how highly acidic water affects the skin and body are covered in Characteristics of Acidic Hot Springs, while how to read the pH indicator is explained in How to Read Onsen pH Values. For the overall picture of spring types, see Hot Spring Types for Beginners. What matters in Kusatsu is entering with the understanding that the water is highly disinfecting, but also strongly stimulating.
Yumomi, Netsunoyu, and the time-bath culture
Kusatsu has a unique tradition called yumomi, in which boards are used to stir hot spring water so it can be cooled to the right temperature without adding water. At Netsunoyu, located right next to Yubatake, the daily Yumomi and Dance Show presents this tradition together with dancing. According to the Kusatsu Onsen Tourism Association, the show is held several times a day in the morning and afternoon, with times varying by season. For visitors who want to understand Kusatsu’s bathing culture in a short time, it is an easy place to include in an itinerary.
Behind yumomi is a bathing method called time-bath. Under the direction of a bath master, bathers enter and exit the water repeatedly for short periods so they can enjoy very hot water without getting overheated. It is a practical tradition born from Kusatsu’s high-temperature, highly stimulating water. Watching the yumomi show makes it clear that this culture is closely tied to the nature of the spring itself.
Sainokawara Rotenburo and how to visit the outer baths
If you value openness, Sainokawara Rotenburo, located deep inside Sainokawara Park on the west side of the onsen district, is an easy choice. After passing through a park where hot water springs up in many places along the riverbed, you reach a large open-air bath that offers one of the widest bathing spaces in Kusatsu and scenery that feels like a highland resort. It is within walking distance from Yubatake, but you should allow a little extra time because you also need time to walk through the park. Opening hours vary by season, and the starting time differs between summer and winter, so it is best to check before visiting.
Another enjoyable option is to tour the communal baths, known as outer baths. Kusatsu has several free communal baths managed by locals, but they are strongly oriented toward local use and the tubs are often quite hot. Some are open to visitors, but the basic style is hot, untreated spring water with little added water, so it is safest to go in expecting a short stay. If you want to relax in a spacious bath, choose Sainokawara Rotenburo. If you want to experience Kusatsu’s hot water and local bathing customs, choose an outer bath.
| Bathing place | Features | Best for | Notes |
|---|---|---|---|
| Facilities and foot baths around Yubatake | Scenic center with easy access | People who prioritize scenery and walking around town | Bathing facilities can be crowded |
| Sainokawara Rotenburo | One of Kusatsu’s largest open-air baths | People who value openness | Requires time to walk through the park; hours vary by season |
| Outer baths (communal baths) | Hot spring water straight from the source, local customs | People who want to experience hot water and culture | Very hot, so long bathing is not possible; locals have priority |
How to enjoy an open-air bath as part of the scenery is also covered in Open-Air Baths in Nature.
Seasonal highlights
Because Kusatsu is at high elevation, the climate changes a lot by season. Summer is pleasantly cool like a highland resort and is a good escape from the heat, while autumn is known for the combination of colorful leaves and rising steam. Winter offers snowy Yubatake and snowy open-air baths, but travel becomes more difficult because of snow and icy roads. It is best to choose your timing based on whether you prefer scenery or ease of movement.
| Season | Highlights | Notes |
|---|---|---|
| Summer | Cool highland air, good for escaping the heat | The elevation means mornings and evenings can be cold, so bring a jacket |
| Autumn | Autumn leaves and steam from Yubatake | It is a busy travel season |
| Winter | Snow-covered Yubatake and snow-view baths | Snow and icy roads can make travel slower |
Kusatsu has its charms in every season, but winter is especially appealing for hot springs, while also requiring proper cold-weather and transport preparation. It is safer to bring one extra layer of clothing regardless of the season.
Bathing precautions
Kusatsu’s water is extremely acidic, so it can irritate sensitive skin or skin with cuts. If you feel discomfort or stinging, get out immediately and do not force yourself to continue. If you are concerned, choose a facility where you can quickly rinse off with fresh water after bathing to reduce the burden on your skin. Strong acid can also damage metal, so rings, necklaces, and other accessories may discolor, and it is safer to remove them before bathing.
You should also pay attention to the high temperature of many baths. In Kusatsu, there is a tradition of using yumomi and other methods to lower the temperature without diluting the spring water, so you are likely to encounter very hot baths. Rather than staying immersed up to your shoulders for a long time, it is safer to bathe briefly several times, taking breaks and hydrating in between. Avoid bathing after drinking alcohol or when you are not feeling well, and be especially careful the first time you try highly acidic water.
Access and how to plan your stay
Kusatsu Onsen is not fully accessible by train alone; you need to transfer to a bus from the nearest station. If you are traveling by rail, Naganohara-Kusatsuguchi Station on the JR Agatsuma Line is the gateway, and the limited express Kusatsu-Shima from Ueno Station to Naganohara-Kusatsuguchi takes about 2.5 hours. From Naganohara-Kusatsuguchi Station, transfer to a JR Bus Kanto local bus, and it takes about 25 minutes to Kusatsu Onsen Bus Terminal. From the bus terminal, Yubatake is only a few minutes away on foot.
A day trip from Tokyo is possible, but if you want to include town walking, multiple baths, and the yumomi show, staying one night makes for a more relaxed visit. By car, you have more flexibility, but in winter you are more affected by snow and icy roads, and roads and parking lots tend to get crowded during peak travel periods. In winter, be sure to check your tires and the weather, and if you are using public transportation, check bus frequency and the last departure in advance.
Kusatsu has long been counted, together with Arima Onsen and Gero Onsen, as one of Japan’s Three Great Hot Springs. It is said that the Zen monk Banri Shuku in the Muromachi period named these three famous springs, and that the Confucian scholar Hayashi Razan in the early Edo period referred to them as the three great springs under heaven. For more on the Three Great Hot Springs and other famous baths, see 10 Famous Hot Springs in Japan. If you are looking for inns or day-use bathing facilities in Kusatsu, we provide an Facility List and a Search Page so you can filter by area and budget.
Frequently asked questions
Can I go to Kusatsu Onsen by train only?
No. You need a bus transfer at the end. Travel by train to Naganohara-Kusatsuguchi Station on the JR Agatsuma Line, then take a local bus for about 25 minutes to Kusatsu Onsen Bus Terminal. The limited express Kusatsu-Shima from Ueno Station to Naganohara-Kusatsuguchi Station takes about 2.5 hours.
Is highly acidic water okay for the skin?
Kusatsu’s water has a pH of around 2, making it one of Japan’s most highly acidic springs, and it has strong disinfecting power, but it is also highly stimulating. Many people can bathe without problems, but sensitive skin or cuts may react. If you feel discomfort, get out right away, avoid long baths, and if you are worried, choose a facility where you can rinse with fresh water afterward.
Can I enjoy it on a day trip?
Yes. Even just walking around Yubatake, bathing once at Sainokawara Rotenburo or an outer bath, and watching the Netsunoyu yumomi show if the timing works will give you a good sense of Kusatsu’s character. However, if you want to enjoy multiple baths and the different atmospheres of Yubatake in the morning and evening, staying overnight is better.
Can you bathe at Yubatake itself?
No. Yubatake is a facility for cooling spring water, not a place for bathing. It is a place to enjoy the scenery and see the source water, while bathing is done at nearby inns, day-use facilities, Sainokawara Rotenburo, outer baths, and similar spots. There is also a foot bath near Yubatake.
Why are the baths in Kusatsu so hot?
Because Kusatsu uses high-temperature spring water without diluting it with water, and lowers the temperature through traditions such as yumomi, in which boards are used to stir the water. As a result, very hot baths are common, and the bathing style called time-bath, where people enter and exit in short intervals to the sound of a call, has been handed down. In hot water, do not push yourself; several short baths are safer.
Summary
Kusatsu Onsen is a famous hot spring resort in Kusatsu Town, Gunma Prefecture, known for its Yubatake scenery, which gushes at about 4,000 liters per minute, and for its highly acidic water around pH 2, one of Japan’s most distinctive springs. Located on a plateau at around 1,200 meters above sea level, it brings together the essential elements of an onsen town around Yubatake, including yumomi, Netsunoyu, Sainokawara Rotenburo, and the outer baths. It also has the prestige of having long been counted among Japan’s Three Great Hot Springs alongside Arima and Gero.
If it is your first visit, simply walking around Yubatake to understand the town layout and limiting yourself to one or two bathing spots is enough to feel Kusatsu’s character. The basics of enjoying Kusatsu are to understand that the water is highly acidic and stimulating, that many baths are very hot, and to avoid long soaking while bathing comfortably and without pushing yourself.
