Flight Haneda Airport departs from Tokyo Haneda Airport at 12:05 and arrives at Seoul Gimpo International Airport at 14:25.
The flighttime is about 2h 20m. The distance travelled ("as the bird flies"): 1450 Km. So the average speed is roughly 621 Km.
The best day to arrive at Tokyo is Monday and it would be best to avoid Tuesday, as prices are on average 196.39% higher than on Monday. (Average prices, based on 392710 datapoints.)
We have a lot more statistics for flights NH 6967 and between Tokyo and Seoul.