Flight Incheon International Airport departs from Seoul Incheon International Airport at 16:25 and arrives at Tokyo Narita International Airport at 19:05.
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 Seoul is Tuesday and it would be best to avoid Sunday, as prices are on average 108.73% higher than on Tuesday. (Average prices, based on 6738958 datapoints.)
We have a lot more statistics for flights OZ 110 and between Seoul and Tokyo.