Hokkaido trip advice

I'm going for a one week drive in Hokkaido in the middle of October. I'm landing in Kushiro and leaving from Sapporo one weak after. I'm looking at guidebooks and websites, but there is so much to see I can't make up my mind... Do you have any recommendation of what we really shouldn't miss? We would like to stay in Eastern or Central Hokkaido. And if anyone has a recommendation for a nice hotel somewhere, don't hesitate!

What are your interests?

I personally love Shiretoko:
http://www.japan-guide.com/e/e6850.html

Other ideas:
http://www.japan-guide.com/list/e1101.html

Thank you for your answer. Sorry for not coming back earlier.
I would like to see mostly nature, if possible partly by the see, but also mountains.
What's the good base to visit Shiretoko?
What about Aikan and Daisetsuzan? Are they really nice?
I hope you can help we chose between all these apparently beautiful places...

Having just taken a trip there, I can say you will be swamped with nature options there. Shiretoko was indeed a highlight for me. Lake Akan, Kussharo, and especially MASHU were nice, and Kushiro Shitsugen, explorable from Kushiro, was also really nice, especially around sunset!

The Japan Guide website does a great job of introducing all of the above except maybe Kushiro Shitsugen, so go to jnto`s website for that.

http://www.jnto.go.jp/eng/location/regional/hokkaido/kusirositugen.html

One of my top highlights from Hokkaido were Rebun and Rishiri Islands, but they are very far from your Kushiro to Sapporo route unfortunately. If you can somehow make it up there though, I would highly recommend it!