Kusatsu Onsen

“Double, double, toil and trouble, fire burn and cauldron bubble”…Surprisingly it was these famous words from the Shakespearean play of Macbeth that came to mind when I first gazed into the Yubatake (hot spring “field”) in Kusatsu Onsen. I had just toiled somewhat over a long journey from Tokyo via 4 trains and a bus, no real trouble, but here I was staring into acquamarine waters, bubbling straight up from the ground, with steam rising and giving off sulfurous fumes. In awe of nature’s beauty and power, I was in for quite an adventure.  So much so, this story will be spread across two blogs.

About Kusatsu Onsen

Kusatsu Onsen is renowned as the top onsen destination in Japan and has proudly held this ranking for 14 years. It is tucked away deep in the mountains in Gunma prefecture and is set in a scenic location with Mt Shirane and the glorious Japanese Alps providing a stunning backdrop. In the winter months it is also a popular ski resort.

The waters are created as the snow and rain which fall on Mt Shirane (an active volcano) sink deep into the ground and are steadily warmed by the magma beneath. It is said that it takes over 30 years for the water to gradually bubble and trickle its way down into the the town of Kusatsu Onsen, providing a very rich, hot source of hot spring water. Unfortunately the access to Mt Shirane is currently closed, however the right hand picture below provides an image of the amazing crater lake.

The natural hot spring water yield in Kusatsu Onsen is over 32,300 litres or more every minute which makes it the most plentiful hot spring in Japan. Yubatake, which is the central feature of Kusatsu Onsen, is a facility designed to cool down the hot water (which at its source ranges from 50-95 degrees celcius) and extract the yunohana which are the mineral components of the onsen water. It is a quite a sight and can only be seen in Kusatsu Onsen.



Magical powers of Kusatsu Onsen

The Japanese have long known the healing power of onsen and appreciate the varying features and powers of each onsen. Kusatsu Onsen however has one of the highest acidity levels, with a pH value of 2.1. This gives it wonderful anti bacterial and other disinfecting properties.


Kusatsu Onsen also gained global noteriety back as early as the Meiji period in 1878 when Dr Erwin Balz, a German specialist invited to Japan to contribute to Japan’s modernisation, praised the medical benefits of hot spring water at Kusatsu. His scientific research has been publishd in German academic journals and his diary written in German, and later published in Japanese and English, led to Kusatsu becoming known around the world.

Disappearing one yen coins and nails!

Beware the powers of Kusatsu Onsen! Due to the high acidity, the aluminium  one yen Japanese coins will dissolve within 7 days and a nail will dissolve in around 9 days if it is left there continuously.



The locals have many unique practices to embrace the powers of the hot spring.  The major goal is to experience the hot springs at their natural best, however as they are so hot they must be cooled prior to bathing. Rather than cooling the waters by adding cold water, a process of yumomi, which involves stirring the water with 180cm long wooden boards to gently cool the water, is used. The exercise of stirring the water, whilst also singing, is meant to be a good warm up activity prior to the bath! Visitors can join in the fun and have a go, and there are also live performances each day reenacting this very traditional practice of Kusatsu Onsen.

Strolling around town

Many of the main features of the town are located within an easy walking distance from the station. Once you have spent some time in the centre at the Yubatake, and had one or two (or more!) baths, there are many little back streets to explore, and enjoy the local delicacies along the way. Robata yaki (slow cooked skewered food cooked over charcoal) traditional home made Japanese senbei (rice crackers), onsen tamago (eggs boiled in onsen water) and onsen manju (steamed buns filled wth bean paste steamed with onsen steam) were a few of the gourmet delights to see and try.


Soba, Sake and Soft Cream

Of the many choices of food and drink along the way, I indulged in soba, sake and soft cream! Soba is a much loved Japanese dish throughout Japan and in regional areas each town often has their speciality. The local sake took my fancy as it was called Bijin -yu, which means beautiful water, suggesting you will become more beautiful if you drink it! Great marketing ploy playing on the tie of sake and the power of the “yu” which is hot spring water. Finally the matcha and vanilla soft cream was a beautiful smooth cool treat after a hot bath.

Night time

The night atmosphere at Kusatsu Onsen was great. Even in the middle of winter, the locals and visitors took to the streets in their yukata and geta that are supplied by the many local ryokan. The Yubatake was also illuminated at night, which added a whole new modern twist to the bubbling cauldron as steam rose to a backdrop of purple or green lighting.

I was extremely lucky to be staying on the night of the inaugural winter fireworks for Kusatsu Onsen. Fireworks are traditionally associated with the summer season in Japan, but it was a terrific experience to see a 30 minute display against the clear dark evening sky at the foot of the ski slopes bordering the town. The day finished with fire and crackle in the sky – a great contrast to the bubbles and steam and lava rocks that had featured at the beginning of the day.


Getting There

The most direct way to access Kusatsu Onsen is via the Limited Express Kusatsu train from Ueno station (2 hours 28 minutes) and transfer to a JR bus (25 minutes). Expressway buses are also available, however beware that the time of 4 hours and 15 minutes can easily stretch to longer depending on traffic conditions.

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