That's a bad way to get to ICN... you might be better off just buying a ticket. HKG/ICN are often both oversold and HKG has a fair share of nonrevs who will all be ahead of you. You will need to pay the departure taxes in NRT for your flight to ICN, however from what I've seen at the xfer desk in NRT, the line is often very long with connecting Asian pax and you might be very tight on time. You can call NWA reservations and they'll give you the load info. Non-NW pilots can't pre-list for a JS.