Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Qatar to Sapporo as you normally would.
Related info for your journey
Useful info, stats and facts about Qatar to Sapporo flights.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Doha Hamad Intl Airport to Sapporo Chitose Airport flight would often be abbreviated as a DOH to CTS flight. Sapporo Okadama Airport (OKD) are other airports near this flight route and their unique identifiers/IATA codes.