Flight Incheon International Airport departs from Seoul Incheon International Airport at 12:15 and arrives at Tokyo Narita International Airport at 14:40.
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 month to arrive at Seoul is September and the most expensive month to fly is June. (Average prices, based on 6618 datapoints.)
The best day to arrive at Seoul is Sunday and it would be best to avoid Saturday, as prices are on average 21.49% higher than on Sunday. (Average prices, based on 4885247 datapoints.)
We have a lot more statistics for flights GA 104 and between Seoul and Tokyo.