Flight Kansai International Airport departs from Osaka Kansai International Airport at 19:35 and arrives at Seoul Incheon International Airport at 21:25.
The flighttime is about 1h 50m. The distance travelled ("as the bird flies"): 1002 Km. So the average speed is roughly 547 Km.
The best day to arrive at Osaka is Saturday and it would be best to avoid Tuesday, as prices are on average 269.08% higher than on Saturday. (Average prices, based on 5037983 datapoints.)
We have a lot more statistics for flights KE 2120 and between Osaka and Seoul.