Hokkaido from tokyo in 3 days?

Hello! I'm travelling with my family around japan for 3 weeks and then I have a final week in japan alone. I'll seperate from my family in tokyo and was looking where I should go from there. I want to spend a bit of that week in the tokyo area doing maybe a side trip up north for a night. The one thing I'm struggling with is should I go to hokkaido? It sounds a great place but I'd only be able to spend 3 days on it max. including the time spent getting there and back overland. Can I even get a whole day in a nature park with that time? Cheers for your help!

If you do want to go to Hokkaido, make sure to fly there and back. It is by far the fastest and generally cheapest way to access Hokkaido. Select an airport that is closest to your destination of choice in order to avoid time loss. Depending on where you go, I recommend to rent a car from the airport.

Which place to go depends on your interests and the time of the year. Outside winter, I recommend Daisetsuzan (Asahikawa Airport) and Shiretoko (Memanbetsu Airport). Three days would be enough to enjoy either of these national parks:
http://www.japan-guide.com/e/e6775.html
http://www.japan-guide.com/e/e6850.html

Alright I'll look into that then! Thanks a lot :D