UA 3851 then UA 1998 at Houston
Seoul → Houston → Cincinnati
Timetable, Houston time
17:54UA 3851 from Seoul at the gate
12:20UA 1998 to Cincinnati leaves the gate
18 h 26 apart on the timetable, overnight
UA 1998 leaves 18 h 26 after UA 3851 arrives on the timetable: more than half a day, so not a connection we count.