Please be aware that Seoul and Tokyo has multiple airports and that these results are for all airports serving the city.
The best month to fly between Seoul and Tokyo is April and the most expensive month to fly is July. (Average prices, based on 1488 datapoints.)
The best day to arrive at Seoul is Thursday and it would be best to avoid Friday, as prices are on average 92.9% higher than on Thursday. (Average prices, based on 208 datapoints.)
The cheapest airline flying from Seoul to Tokyo is Jin Air. They are 67% cheaper than Japan Airlines. (Average prices, based on 1505 datapoints.)
The best time to fly is at around 13. (Average prices, based on 1766 datapoints.)