It must be Nagano prefecture. It takes 2hours and half by bullet train from Shinjuku to the central St. of Nagano, which is called Matsumoto. Hakuba is the famous skiing area, and it's 1 hour away from Matsumoto by train.
When I went skiing in Hokkaido, I discovered the quality of snow is totally different from my experience in other ski resorts such as Niigata (Yuzawa), Fukushima (Inawashiro), etc.
I went to KIRORO resort (https://www.kiroro.co.jp/), takes only about an hour from central Sapporo. The snow was powdery, fluffy, and did not hurt at all even if you fall down.
Niseko seems to be the most popular ski resort in Hokkaido but I've never been there. I heard the area is very popular to Australians.