Flight Haneda Airport departs from Tokyo Haneda Airport at 19:45 and arrives at Seoul Incheon International Airport at 22:05.
The flighttime is about 2h 20m. The distance travelled ("as the bird flies"): 1487 Km. So the average speed is roughly 637 Km.
The best day to arrive at Tokyo is Sunday and it would be best to avoid Saturday, as prices are on average 321.54% higher than on Sunday. (Average prices, based on 1278065 datapoints.)
We have a lot more statistics for flights KE 2104 and between Tokyo and Seoul.
NZD