I had never heard of this airline before. Jeju Air is a low cost carrier based in the city of Jeju, South Korea. It operates an all Boeing 737 fleet of 14 aircraft.
"LOTTE Duty Free" logojet.
The "Lotte Duty Free" advertisement and ETOPS marking are clearly visible.
The newest and also the second lojojet for Jeju Air, “Lotte Duty Free”, seen here approaching 25R. The weather wasn't great but at least it was sunny.
The latest special livery of Jeju Air promoting the In-flight Duty Free! "JEJU 2109" final approach rwy 25R from Seoul/Incheon in the afternoon.