Flight Gimpo International Airport departs from Seoul Gimpo International Airport at 19:40 and arrives at Tokyo Haneda Airport at 21:45.
The flighttime is about 2h 05m. The distance travelled ("as the bird flies"): 1450 Km. So the average speed is roughly 696 Km.
The best day to arrive at Seoul is Sunday and it would be best to avoid Monday, as prices are on average 97.35% higher than on Sunday. (Average prices, based on 1506285 datapoints.)
We have a lot more statistics for flights JL 94 and between Seoul and Tokyo.