For Australian residents Japan Snow Accommodation reccomends Sure Save for your travel insurance needs. 

As well as covering all medical events covered in the standard policy Sure Save offer a range of benefits for travellers participating in a winter sport in Japan when they purchase the "winter Sports Option" 

Snow specific inclusions include

Skiing and snowboarding (on piste and off-piste) on groomed and ungroomed runs and marked trails patrolled/monitored by resort authorities.

Back country skiing and snowboarding only when on a guided tour with a licensed tour.

Heli-skiing and cat skiing only when on a guided tour with a licensed tour operator.

Toboganning on marked trails, on-piste only on marked trails.

Cross country skiing on groomed and ungroomed runs and marked trails patrolled/monitored by resort authorities.

Snowmobiling when provided by the recognised piste authority to and from areas designed for recreational skiing within resort boundaries, or recreational skiing within resort boundaries, or when on a guided tour with a licensed tour operator.

Telemark skiing Telemark skiing within the resort and terrain park boundaries on  groomed and ungroomed runs and marked trails patrolled or monitored by resort authorities 

When you cant ski or board the wintersports option covers pre paid costs such as eqipment hire, lift passes & ski school costs if you are injutred in an accident or suddenly fall ill and cant ski for more than 24 hours. 
Equipment cover while skiing & snowboarding. SureSave's Winter Sports Option covers your winter sports equipment for its depreciated value up to $700 per item for all luggage events, even while in use, up to your plan limits. If it is accidentally damaged, it's covered provided it's less than 3 years old. 
Options to cover cancellation expenses from $5,000 to an unlimited amount.

Please remember that you need to chose travel insurance based on your individual sitiuation & it is extremely important that you read the Policy Disclosure Document cleary and are condfident it suits your needs before purchasing travel insurance. While we have done our best to ensure the accuracy of the information you must base your decision 100% on the information provided direct from your travel insurance provider when you purchase travel insurance.

Click on this Sure Save Link to get a full list of benefits available & an instant quote based on your needs. The winter sports coverage is on page 23 of the policy disclosure ducument. For winter sports coverage you will need to select this option when purchasing your cover.

For worldwide residents Japan Snow Accommodation reccomends World Nomads. Please click on the on this World Nomads link to go through to the instant quote calculator.