You need to add in a read command to show it in D-Menu, this needs to be added to CruelDragonMir3G.txt and has to read from SQL. You will also need to add a script into MapQuest.txt, that tells the script that once KM is dead it adds a point into SQL for the Key and not actually give you an item.
Have a look at the Guild Bank Script, you will also need to use the #CALL command to read it in CruelDragonMir3G.txt