NH 8421 then WE 502 at Narita
Chicago → Tokyo → Seoul
Timetable, Tokyo time
18:38NH 8421 from Chicago at the gate
13:25WE 502 to Seoul leaves the gate
18 h 47 apart on the timetable, overnight
WE 502 leaves 18 h 47 after NH 8421 arrives on the timetable: more than half a day, so not a connection we count.