CASE sentence for SQL query
You haven't specified what happens for values other than '기아' ('KIA') and '현대' ('HyunDai').
Try

SELECT
CASE
    WHEN Maker='기아' THEN 'KIA' 
    WHEN Maker='현대' THEN 'HyunDai'
    ELSE Maker
END AS new_Maker


FROM table_name