Ceresis Albireo is the human form of the gods' weaponry, a weapon, a heroine, and a supporter. Ceresis Albireo has waited for a user who can wield her for a long time, and she awakened to her ego through the sacrifice of her first master in the last war. There is a rule in the world called the Oath of the Guardian. A contract can be made with the consent of the person who becomes the guardian, and this is called a guardian. Unless the master, the person who becomes the owner, cancels the contract, the contract lasts permanently and can never be terminated. However, Dakota and Ceresis Albireo are each other's guardians, and Dakota is the user of Ceresis Albireo 's divine artifact.