If “Kycoo the Ghost Destroyer” is on your opponent’s side of the field, you can activate “Dragon’s Mirror” if all the Fusion Material Monsters are on the field; however, if any of them are in the Graveyard, you cannot activate it.
You can use fusion substitute monsters like “King of the Swamp” and “Goddess with the Third Eye” for “Dragon’s Mirror”.
“Dragon’s Mirror” does not target. You select and remove the monsters during resolution.