The shortest route for ICN-NRT is probably via TPE on CX - CX421 goes ICN-TPE, arriving at 11:00, connecting with CX450 departing 12:45 TPE-NRT. Unfortunately the connections aren't so great travelling in the other direction, requiring an overnight stay if you were to go that way. It shaves about 900 miles off going via HKG, which hopefully helps!