Flight Kansai International Airport departs from Osaka Kansai International Airport at 14:10 and arrives at Seoul Incheon International Airport at 16:20.
The flighttime is about 2h 10m. The distance travelled ("as the bird flies"): 1002 Km. So the average speed is roughly 462 Km.
The best day to arrive at Osaka is Thursday and it would be best to avoid Sunday, as prices are on average 1051.37% higher than on Thursday. (Average prices, based on 6327506 datapoints.)
We have a lot more statistics for flights JL 5271 and between Osaka and Seoul.