Flight Narita International Airport departs from Tokyo Narita International Airport at 16:25 and arrives at Seoul Incheon International Airport at 19:10.
The flighttime is about 2h 45m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 565 Km.
The best day to arrive at Tokyo is Wednesday and it would be best to avoid Tuesday, as prices are on average 1397.56% higher than on Wednesday. (Average prices, based on 4218055 datapoints.)
We have a lot more statistics for flights NH 6973 and between Tokyo and Seoul.