North or/and South?

Hi,
I'm planning a trip in Japan. I will stay in Tokyo for awhile because I have to and will visit Nikko but then what else. I'll be heading out on the 16th of Feb.
I was thinking to head north. Fly to Sapporo and explore Hokkaido. How many days should I spend there? And what to see?
Might fly back to Tokyo on then head down to the South via Nagoya, Hiroshima to Beppu (I have visited Kyoto and Nara) and then fly back home from Osaka begining of April. What else should I include? I would like to explore the traditional culture, onsen and nature.
Thanks for help
:) K

You are going to miss the snow festival in Sapporo by a few days ( ends 11/2 ) You could fly through to Abashiri and do the ice cruise. Spend a night and do the train trip along the coast to Shiretokoshari. Take the special train "Okhotsk No Kaze" ( Sea Ice Express) back to Sapporo. It departs at 1417 and arrives at 1937. Seats in the front car are a must. The scenery is spectacular. A little time to see Sapporo and perhaps Otaru then .......