Please be aware that Seoul has multiple airports and that these results are for all airports serving the city.
The best month to fly between Seoul and Manila is March and the most expensive month to fly is December. (Average prices, based on 1076 datapoints.)
The best day to arrive at Seoul is Saturday and it would be best to avoid Monday, as prices are on average 28.74% higher than on Saturday. (Average prices, based on 1002 datapoints.)
The cheapest airline flying from Seoul to Manila is Cebu Pacific Air. They are 61% cheaper than Korean Air. (Average prices, based on 1084 datapoints.)
The best time to fly is at around 23. (Average prices, based on 2093 datapoints.)