Astarotte's Toy

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.

Naoya is introduced to Astarotte, but she refuses to get along with him. Naoya learns that when Astarotte was young, she witnessed her mother, Mercelída Ygvar I, engage in intimate acts with a member of her harem. From this, she developed a dislike for men and grew distant from her mother. Wanting to be able to make her feel less alone, Naoya makes a replica of Astarotte's favourite doll. The next day, Astarotte agrees to accept Naoya into her harem, on the condition that he be her 'toy'.

Naoya brings his ten year old daughter, Asuha, to the Creature World. Upon learning their ages, Astarotte grows upset since it would mean he had sex when he was twelve, though Asuha is quick to jump to Naoya's defense. Wanting to apologise to her, Asuha enrols into Astarotte's school, where she makes some new friends, Mist, Yuna and Lucca, who mention they haven't had the courage to be friends with Astarotte. As Asuha makes up with Astarotte, rumours spread about a 'human male' on campus, which turns out to be a rampaging llama from a zoo. As it goes wild, Mist, Yuna and Lucca step in to defend Astarotte before Naoya manages to calm it down. Afterwards, Astarotte manages to make friends with the other girls, who nickname her 'Lotte'.

The school's students receive invitations for their parents to attend a parent-teacher party. Astarotte states her mother, Mercelída, would be too busy to attend, but Asuha insists that she go ask her in person to be sure. She and Zelda visit Mercelída's palace, but after hearing the muttered complaints of palace staff, Astarotte returns home, leaving the invitation behind. At the party, Astarotte teases her rival, Elika, about Astarotte's alleged relationship with Naoya, but later becomes saddened when Mercelída doesn't show to the party. Her mother, who had come late to the party was returning to her own palace after missing her daughter, decides suddenly to see Astarotte anyway and flies to Astarotte's palace, only to encounter Naoya and Asuha, who is revealed to be her daughter, also known as Asuhariet.

Naoya feels conflicted by the appearance of Mercelida, who three years after their chance fling left Asuha with him and disappeared, with Mercelida immediately running off before listening to what Naoya has to say. Judit reveals to Naoya that Mercelida is the queen, making Asuha and Astarotte half-sisters, and asks him to keep it a secret from Astarotte. Wanting to speak with Mercelida, Naoya and Asuha sneak into the palace dressed as maids. They are discovered by one of the queen's servants but is coincidentally chosen to be an escort based on Mercelida's requests. Upon meeting her, Naoya gives his thanks to Mercelida for bringing Asuha into his life. As Naoya talks with Mercelida, it is revealed she hid Asuha in the human realm to avoid the same battle against sisters for the throne that she faced. Noticing Astarotte is still downhearted, Naoya asks Mercelida to visit her class for the day, making it a day where everyone's parents could visit. Afterwards, Astarotte and Mercelida manage to reconcile with each other.

As Astarotte receives tickets to an amusement park, she becomes irritated with everyone making use of Naoya. Later that night, Astarotte goes missing before Naoya finds her by the World Tree. As Astarotte yells at Naoya, she accidentally activates the gate and is sent to the human world. Trying to think of a way to get her back, Naoya and Asuha go to seek out a sage named Sorveig that could help them. In order to see her, they have to solve a riddle, which Asuha manages to answer with her undies. There, they meet the sage, Ingrid Sorveig Sorgrims, who reveals the gate is linked to the Succubus race. As Ingrid agrees to help them, she soon learns that, due to the lack of magic in the Human World, Astarotte doesn't have enough magic to activate the gate.