We have two separate Korean Air Tickets, one from Boston to Seoul we booked using Virgin Atlantic Points, the other from Seoul to Tokyo we booked directly on Korean Air's website. There is a 4 hour layover between flights. Will Korean Air be able to through-check the luggage to Tokyo in Boston even though the flights were booked separately? Will the check in counter in Boston also be able to check-in and print boarding passes for the Seoul to Tokyo flight? If not, will 4 hours be enough transit time in Seoul to go through immigration and re-check bags?