Flight Narita International Airport departs from Tokyo Narita International Airport at 13:20 and arrives at Seoul Incheon International Airport at 15:55.
The flighttime is about 2h 35m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 602 Km.
The best day to arrive at Tokyo is Wednesday and it would be best to avoid Tuesday, as prices are on average 53.81% higher than on Wednesday. (Average prices, based on 4425883 datapoints.)
We have a lot more statistics for flights OZ 101 and between Tokyo and Seoul.
