Please be aware that Tokyo and Seoul has multiple airports and that these results are for all airports serving the city.
The best month to fly between Tokyo and Seoul is January and the most expensive month to fly is May. (Average prices, based on 923 datapoints.)
The best day to arrive at Tokyo is Tuesday and it would be best to avoid Saturday, as prices are on average 62.52% higher than on Tuesday. (Average prices, based on 767 datapoints.)
The cheapest airline flying from Tokyo to Seoul is EastarJet. They are 58% cheaper than Korean Air. (Average prices, based on 968 datapoints.)
The best time to fly is at around 11. (Average prices, based on 1905 datapoints.)