From the website, filtered through Google translate (and tweaked):
In a place created by the imagination, ruled by magic where the heroes are not the protagonists of legends, lives Minimonfa (Mini Monsters Fantasy), the army of the smallest and cutest monsters ever. They are captured by the Archmages, and are raised and made more powerful to defend the dark rooms of the dungeons where the bosses keep their rich treasures.
Become an Archmage, build your dungeon full of monsters and deadly traps and snares, and send your heroes to conquer the enemy dungeon. But remember that you will not be alone -- the Minimonfa are waiting to fight you.