Snowshoe tour
Great winter activity if you do not ski/snowboard or if you just want to try something different. Half / full-day/ evening, private / group tours available.
Website: https://www.evergreen-backcountry.com/snowshoe-tours/
Snowmobile
For a short outdoor activity look at this one hour snowmobile tour. Tandem and single rides available. Free accommodation pick-up. Price: 9,000-12,000 yen per person.
Website: https://hakuba.lion-adventure.com/en/activity/snowmobile/