Buses from Lake Akan to Lake Kussharo/Mashu

I would like to visit Lake Akan and also Lake Kussharo and Mashu but wonder if there are any buses directly connecting these two regions of Akan NP? I saw some links from helpful people in some of the threads but the links are no longer active. Does anyone know of buses connecting these 2 regions? If not, the best option I see is for me to visit Lake Kussharo/Mashu (from Kushiro by train), then visit Shiretoko NP and then take the train to Kitami. From there, I have seen schedules for buses to Lake Akan.

Unbelievably, there are no regularly scheduled buses between these two parts of the national park (Akan is probably Japan's worst national park when it comes to public transportation). What exists is a scheduled sightseeing bus during certain times of the year:
http://www.akanbus.co.jp/sightse/s001.html

Thanks, Uji. But I cannot read Japanese. I have another question. I'm visiting Hokkaido in mid October. Any chance to still see flowers at that time and where would you recommend if they are in bloom?

Oct is the month for autumn colour in Hokkaido. In average year early to mid Oct is good for koyo in Sounkyo Gorge. By mid Oct it will move south to Jozankei and Niseko and by late Oct it would be around Onuma Quasi National Park and Hakodate.

Driving from Sounkyo to Sapporo during early-mid Oct we still saw some colourful outdoor flower fields in the Hills of Zerubu and Atom in Biei and Farm Tomita in Furano.