Great terrain, a lot of touring, monkeys, hot springs, karaoke and really nice parks.
We had some bad luck with the snow when we went, not a single powder day for 2 weeks. I have spnt a total of 4 weeks in Japan and still haven't skied pow there...
First two weeks was ice, rain and more ice. Second time around we got some snow on sunbaked hardpack. We still had a blast both times though. Japan is one of the best places in the world imho (generally speaking).
OP if you get the opportunity, go, you won't regret it. Do you have any specific questions?