12 Day Hokkaido Trip Itinerary

Here's a rough outline of my trip:

https://i.ebayimg.com/00/s/NDA2WDgwMA==/z/WM4AAOSwL4JdZUyX/$_59.JPG

I will be flying from Tokyo <-> Sapporo.

Day 1 (Oct 12) - Tokyo (8PM)
Day 2 (Oct 13) - Morning flight to Sapporo, stay in Sapporo
Day 3 (Oct 14) - Sapporo - Otaru Side Trip
Day 4 (Oct 15) - Sapporo - Furano - Asahikawa
Day 5 (oct 16) - Asahikawa - Utoro
Day 6 (oct 17) - Shiretoko National Park
Day 7 (oct 18) - Shiretoko National Park
Day 8 (oct 19) - Akan National Park
Day 9 (oct 20) - Akan National Park
Day 10 (oct 21) - Kushiro Wetlands - New Chitose
Day 11 (oct 22) - New Chitose - Noribetsu/Lake Toya
Day 12 (oct 23) - Lake Toya - Sapporo
Day 13 (Oct 24) - Tokyo
Day 14 (Oct 25) - Tokyo -> Singapore

Roughly based my itinerary on this site here: https://www.nomadasaurus.com/hokkaido-itinerary/

Does anyone have any comments on which areas we should spend more time on? Mainly coming for the fall foliage/koyo chasing, some scenic drives and the seafood cuisine.

We will be renting a car from October 15-23 to do the road trip leg of it.

You have Asahikawa and Furano in the list but not Biei. It is 20 mn from Asahikawa. In my view, it has some of the best landscape in the entire Hokkaido. I have been there few times in the winter (https://bizarrejourneys.com/hokkaido-in-winter/) so not very familiar with Autumn foliage but would imagine it to be as splendid. It is a small town with few but nice dining venues, a photography studio as well as nice little train station.

Thank you for the recommendation! I will add Biei to my list.

In terms of day allocation, is this enough?

If autumn foliage is the main objective instead of Eastern Hokkaido consider doing the western and southern part of Hokkaido. In average year mid Oct is the foliage season just south of Sapporo and places good for enjoying koyo include Jozankei, Houheikyou Dam, Niseko, Shikotsu-ko and Noboribetsu. By late Oct it would be nice to go further south to Onuma Quasi National Park, Miharashi Park and Hakodate.