Hokaido Trip from 2 Dec - 9 Dec plan

Dear ,
I had booked a flight to Hokkaido (New Chitose ) from 2 Dec.(Arrival ) ~ 9 Dec.(Departure) .
Is there any suggestion for me to plan the trip - Using 7 days train pass.
- 2-Dec. -
- 3-Dec. -
- 4-Dec. -
- 5-Dec. -
- 6-Dec. -
- 7-Dec. -
- 8-Dec. - move to New Chitose - Grand Terrace hotel.
- 9-Dec. - Depart back on early flight
Thank you in advance if any advise is welcome .

I spent the last winters a couple of week in Hokkaido, a week around Biei (the trees) and 10 days around Shari (the lakes and the ocean) ; we had a rental car both times and had no problems driving in the snow and ice. We looked in using trains in Hokkaido but went for a rental car instead, especially since booking it in combination with hotel and flight was cheap.
I especially loved the several small onsen we visited: http://monochrome.me.uk/news/kotan-onsen/ and I would certainly recommend that you find some nice onsen hotel or onsen for you to spend time at while in Hokkaido.