Visiting Japan for a ski holiday is very easy for most people. Citizens of many countries do not need a visa at all to enter Japan, providing they are staying less than 90 days/3 months and will not be working. They will be given an entry permit on arrival at Narita Airport (They are required to have a flight/boat booked out of Japan, and may be asked to show on onward bound ticket). For countries not listed below you may need to get a visa in advance-please consult Japan's Ministry of Foreign Affairs website.
If you are not just coming to Japan for a ski holiday, but also want to do some work, working-holiday visas for 6 months to Japan may be granted to citzens of the following countries; Australia, New Zealand, UK, Canada, France and Germany provided that they are between the ages of 18 and 25 ( up to 30 yo in some cases). This visa can be extended twice once you are in the country, for a total period of 18 months. For more information please see the Japan's Ministry of Foreign Affairs working holiday page