Best of Hokkaido

Hello! I'm planning a trip in Hokkaido where i want to see all,not just the most "famous" city or parks,but i would like to see the hidden/uncommon places too
at the moment in my trip there are:
1 Hakodate
2 Otaru
3 Sapporo
4 Furano & Biei
5 Asahikawa
6 Noboribetsu
7 Akan
8 Tokachi
9 Shiretoko
10 Wakkanai

what sould i add? i have no time limit to stay there,so please,help me planning the best holiday in Hokkaido that can i have

thanks

When?
How? (car? bike? train? walk?)
How many days?
What want to do?

https://www.jnto.go.jp/eng/location/regional/hokkaido/
http://northern-road.jp/navi/eng/index.htm

Around April
Train and car
No time limit
Everything; nature,technologies,culture,festival ecc

Around April

I am sorry to say April is one of the worst month to visit Hokkaido (another worst month is November).

Snow is beginning to melt but there are some non-photogenic remnants. No flower, no green. Wind is strong and the weather is still cold. There is winter beauty in January and February and spring comes in May. Of course summer months (June to August) is nice.

Okay thanks,so probably ill choose another month,maybe May/June
Do you have some cities or places uncommon to visit?

If you can visit at any time - visit in late June early July. Include Rishiri and Rebun Islands if you like nature. Noboribetsu also has some of the best onsen waters in Japan. Stay at the Daiichi there - it's one of only three hotels I suggest in Japan. You don't stay here for the hotel - but for the onsen theme park. Ashihakawa is nothing special, apart from the Zoo and it's close proximity to the Daizatsuzan (spelt wrong I know) National Park

Do you have some cities or places uncommon to visit?

You might better start on late May since early May is still cold especially in the northern part of Hokkaido. Start with Wakkanai or Rishiri. There are flights from Tokyo Haneda to Wakkanai and Sapporo to Rishiri. These flights are rather cheap for the foreign tourists.

https://www.ana.co.jp/en/us/promotions/share/experience_jp/

View of Mt. Rishiri from Rebun island is one of the most beautiful in Japan. But it depends on the weather so you might better spend several days/nights there. You can go to Rebun from Wakkanai or Rishiri by ferry.

http://www.heartlandferry.jp/english/

After Rishiri/Rebun take rental car and drive through the north eastern coast to Abashiri. This route is called "Okhotsk line". Along the way you can see some lakes (Kuccharo, Saroma, Notoro and Abashiri). Then drive to Shiretoko. Mt Sharidake is very beautiful. There are some lakes and mountains like Kusshraro, Mashu, Akan and On-neto lakes and Mt Me-Akan, Akan-Fuji and Io-zan. These places are called Do-to meaning east HokkaiDO.

After Do-to, go back to the central Hokkaido where the highest mountains in Hokkaido exist. These mountains are called Daisetsuzan as a whole and the highest peak is Asahidake. You can take ropeway from Asahidake onsen. Drop car at Asahikawa and then take bus to Sapporo where you can side trip to Otatu.