Flight Haneda Airport departs from Tokyo Haneda Airport at 12:05 and arrives at Seoul Gimpo International Airport at 14:40.
The flighttime is about 2h 35m. The distance travelled ("as the bird flies"): 1450 Km. So the average speed is roughly 561 Km.
The best day to arrive at Tokyo is Tuesday and it would be best to avoid Thursday, as prices are on average 130.01% higher than on Tuesday. (Average prices, based on 506802 datapoints.)
We have a lot more statistics for flights OZ 1075 and between Tokyo and Seoul.