Takeru, a “Nurturer,” who was born into a family that trains monsters. To make money, he accepts requests from the Demon King and works hard to raise vicious monsters. One night, a wounded witch visits him and asks him to train Anna, a young girl. In fact, Anna is the last survivor of a legendary witch family… Will a bond be formed between Anna, whose ultimate goal is to destroy the world, and Takeru, the best “Nurturer” in the demon world? What will become of the world?