Mt. Shirane (草津白根山) is located in Kusatsu, Gunma Prefecture. It is 2160m high and active volcano. There are many spots you can see the active volcanic action in this mountain, and some of them are very dangerous to see it. In Mt. Shirane, snow stays until middle of May. One of the popular hiking spots.
Tourist Info
There are many restricted area. Stay away from those dangerous spots.
Access
0. Kusatsu
1. use bus to Kusatsu Shirane Resthouse.
1 hr.
New Wave Samurai Movie. 
映画好き集まれ！ 
Because there are many Mt. Shirane in Japan. This one is also called Kusatsu Shirane Mountain. It is the active volcano and there are many volcanic activities. The last eruption was 1983.
Lake Yugama
... is a caldera lake located on the top of Mt. Shirane. It is one of the popular spots in Mt. Shirane. It has the strongest acid water in the world.
There are many caldera lakes on this mountain.