Flight Narita International Airport departs from Tokyo Narita International Airport at 19:50 and arrives at Seoul Incheon International Airport at 22:50.
The flighttime is about 3h 00m. The distance travelled ("as the bird flies"): 1555 Km. So the average speed is roughly 518 Km.
The best day to arrive at Tokyo is Thursday and it would be best to avoid Sunday, as prices are on average 399.79% higher than on Thursday. (Average prices, based on 4214208 datapoints.)
We have a lot more statistics for flights 7C 1122 and between Tokyo and Seoul.
