MySQL : How to fill in empty data with custom text
You must convert your values list to rowset.
For example:
SELECT
   city,
   area.region,
   area.postcode
FROM ( SELECT 'Jakarta' city UNION ALL
       SELECT 'Jabodetabek' ) cities 
LEFT JOIN area USING (city)

This query will give NULL for the row for which there is no city value in area table. If you need some custom string literal then use COALESCE() function, i.e. not SELECT city, ... but SELECT COALESCE(city, 'Empty') city, ....

Depends on MySQL version you may use another methods: ROW() function, JSON_TABLE() function, etc.