From Athens, you need to get to South Korea. There are no direct flights so you've got to change somewhere. Although it might look strange on a map, I suggest travelling via Rome. It's just a short, dirt cheap, flight there with Aegean Airways. This now means that you can buy a return ticket from Seoul to Rome (which is likely to save you quite a lot of money). As I read your post, your friend is travelling to South Korea with you so, of course, he/she will need to purchase a single (but see below).
Your friend now needs to get back from South Korea to the USA. It's difficult to give exact suggestions without knowing exactly where your friend lives but it seems obvious that the quickest route would be to fly eastwards. However, if your friend's not in a hurry, it might be worth comparing the total costs of single flights, from USA to Rome to Seoul to USA, with the alternative of buying return flights from the USA to Rome and from Rome to Seoul. Of course, that means returning home 'the long way round' but it deserves consideration. (If your friend really isn't in a hurry, he/she could have a few days on his/her own, in Rome, to break up the flight).
OK. Those are my first thoughts. If you want me to 'put some flesh on the bones', I'll need further information such as your planned travel dates and your friend's location in the USA. You can mail me at
[email protected]
Chris