So to get this straight, you're flying North America-ICN-NRT-HND-East Asia? Have you considered ditching the last two legs and just flying direct from ICN to wherever you're going (if there's a flight to it from HND, there's almost certainly one from ICN as well, quite possibly on a low-cost carrier), or at least seeing if you can change ICN-NRT/HND into ICN-HND or ICN/GMP-HND? Incheon to Gimpo is a quick 30-min train trip, vs. the multi-hour Narita to Haneda odyssey.