There are four airlines offering flights to Sapporo. The most direct route isn’t necessarily the cheapest – being flexible is key to finding the lowest airfare rates. For example, try searching by month to see the best time of the week to fly. The cheapest date is currently 08 / Mar / 2019.
Make sure you use the search options above to search for flights to other airports in Sapporo, not just New Sapporo International Airport. The more options you look at, the better your chance of finding a cheap deal. Just so you know, the flight typically takes 19 hrs 5 mins.
If you're planning on going to Sapporo during this time, you could take a look at other airport options. Or you could try to get a last-minute bargain.