Succubi are a race of beings who survive by having a harem of men from which they can suck 'life essence' from. However, Astarotte Ygvar, the crown princess, hates men. Under relentless pressure from Judit, her chief of staff, to grow up and start building her harem, she agrees to start but only with a human male. In the Creature World, humans are considered mythical creatures, with none having been seen in a thousand years. To her dismay, Judit manages to travel to the human realm and return with a 23-year-old human male named Naoya Tōhara, who accepts the offer to found Astarotte's harem.