Flight Narita International Airport departs from Tokyo Narita International Airport at 13:55 and arrives at Seoul Incheon International Airport at 16:35.
The flighttime is about 2h 40m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 583 Km.
The best day to arrive at Tokyo is Thursday and it would be best to avoid Sunday, as prices are on average 354.5% higher than on Thursday. (Average prices, based on 3826453 datapoints.)
We have a lot more statistics for flights 7C 1105 and between Tokyo and Seoul.
THB