What date are you looking for the fare? I do know that demand for Hokkaido from HKG/TPE fluctuates seasonally. Fares do go up and down depend on season. CTS is the most common arrival airport to Hokkaido with most number of international flights. I will not be supersize to see CTS fare fluctuate more than fares to other airport such as HKD.
As for international flight between HKD and Far East Russia, former Sakhalin Airlines (SAT Airlines, HZ, currently Aurora Airlines) used to operate HKD-UUS (Yzuhno-Sakhalinsk) using An-24 then later DHC-8. The switch from An-24 to DHC-8 was part due to new regulations implemented in Japan on 2007 requiring commercial aircraft to be equipped with TCAS. Then further later HKD-UUS was switched to CTS-UUS. Currently there is no Sakhalin route from HKD.