Flight Incheon International Airport departs from Seoul Incheon International Airport at 15:05 and arrives at Tokyo Narita International Airport at 17:30.
The flighttime is about 2h 25m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 643 Km.
The best day to arrive at Seoul is Friday and it would be best to avoid Thursday, as prices are on average 169.5% higher than on Friday. (Average prices, based on 6801992 datapoints.)
We have a lot more statistics for flights 7C 1107 and between Seoul and Tokyo.