Rescue Insurance is Compulsary.
All customers MUST have their own mountain rescue insurance which covers mountain helicopter rescue, hospitalization and repatriation to their home country. This is your responsibility. You will be required to provide proof of insurance before attending any tour.
Travel insurance seldom covers all of this. Even if your travel insurance has special cover for "off-piste" or "guided backcountry", it probably does not cover helicopter rescue, or may require you to contact the insurer before calling a helicopter, which is not practical.
We will not arrange short-term local insurance on your behalf as it seldom covers non-Japanese residents. And becasue you have no chace to review the policy fineprint. And because in the event of a claim, you would have to read and write Japanese to correspond with the insurer.