If you want to see snow monkey? Jigokudani is one of the best place you can see Snow Monkey. Snow Monkey in Jigokudani enjoy Onsen, and they look really relaxing especially in heavy snow in winter.
The Boss Monkey in this park is named "Ryuou," the king of Dragon.
Japanese Macaque, a.k.a. Snow Monkey
... is one a native species of Japan, and only monkeys which live in cold weather with snow. They survive winter temperature below - 15 degree celsius, 5F. In Japanese, they are called "Nihonzaru." Japanese Macaque lives in mountains area of Honshu. The most notable things for Japanese Macaque is that they enjoy Onsen like human.