Flight Narita International Airport departs from Tokyo Narita International Airport at 19:25 and arrives at Seoul Incheon International Airport at 22:00.
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 Monday and it would be best to avoid Friday, as prices are on average 97.15% higher than on Monday. (Average prices, based on 3797697 datapoints.)
We have a lot more statistics for flights 7C 1107 and between Tokyo and Seoul.