But apart of Kusatsu, Gunma Prefecture has another hot spring spots that recomended to try at least once; Ikaho Onsen and Shima Onsen. Ikaho Onsen located in Shibukawa City, Gunma Prefecture. And Shima Onsen is a part of Nakanojo City of Gunma Prefecture. This time I would like to introduce the forty-thousand hot spring or Shima Onsen (四万温泉).
If you're a fan of Studio Ghibli, you must familiar with one of their famous animation Spirited Away or in Japanese 千と千尋 (Sen-to-Chihiro). A building in Shima Onsen is one of the model of the animation's hot spring design.
Here is the real building
It basically means "accumulation of good deeds building" or Sekizenkan. The building itself is actually a real ryokan, so you can stay a night in there for a pricey night or maybe just a higaeri-onsen (day trip) starting from 1200¥/adult. This is the ryokan's website:
The hot spring water in Shima Onsen is translucent clear. Totally different from Kusatsu, but it has a lot of mineral and you can drink the hot spring water (飲泉=Insen or onsen water used for medical treatment) directly from the fountain available near the ryokan.
Additional info: there's a Hello Kitty Cafe near Sekizen Ryokan. You can enjoy Hello Kitty pancake for around 600~800¥.
Beside Sekizen Ryokan I mentioned above, there is a really cheap day-trip onsen located around 2km from Sekizen Onsen; 四万清流の湯 (Shima Seiryū-no-yu). You can walk from Shima-onsen bus stop for about 26min or 6min by car.
For only 500¥/adult/2 hours you can wash your body and enjoy both indoor and outdoor hot spring.
Here is the link: http://www.nakanojo-kanko.jp/onsen/shima-seiryu.shtml
Although it's really cheap, but the place are clean and you can enjoy drinkable hot spring water and free drink for free too. I really recommend both of Sekizen Ryokan and Shima Seiryū Onsen if you have free time to visit Gunma Prefecture.
You can take highway bus from Tokyo Shinonome or Tokyo Station Yaesu-dori to Shima Onsen for 3.100¥/one way.
http://shimaonsen.com/campaign/busplan_list (Japanese only)