Hiking in Hokkaido national park

Hello,
I am planing a trip to Hokkaido, late June to early July. I want to rent a car and visit some national parks like Daisetsuzan, Akan and Shiretoko, maybe do some 1 or 2 days hiking trips.

I am not that secure about the best way to do it, like if you can do most of the trails by yourself or if it is best to book some kind of tour.

I know that on Shiretoko that might be the best solution, because of bears and so, but for example on Daisetsuzan, is it really necessary, or would it be fine to go alone?

I have been having some difficulties finding companies that can arrange a one day hike, most of the ones that I have found are long tours for 5-8 days.

Hopefully someone can give some good tips.

Thanks

I have been looking at this hike myself: https://japanhike.wordpress.com/2008/08/21/mt-shari/

I stayed at the hotel in Kiyosato this winter and was told that Mt Shari is a popular hike and it looked really great. http://www.ryokuseisou.com/