Ten-year-old fourth grader Sakura Kinomoto opens a mysterious book in her father's study and accidentally releases the magical Clow Cards. Created by the half-English half-Chinese sorcerer Clow Reed, the Clow Cards were sealed within the Clow Book upon his death and represent a combination of magic from Clow's mixed heritage. Each card has its own personality and characteristics and can assume alternate forms when activated. Cerberus, the guardian Beast of the Seal, awakens and emerges from the book's cover. Upon learning the cards are gone, he tells Sakura that she must have special powers, and that is now her responsibility to retrieve the missing cards. As she finds the cards, she must battle its magical personification and defeat it in order to seal it away. Cerberus acts as her guide and mentor throughout the quest, while her classmate and best friend Tomoyo Daidouji films her exploits and provides her with costumes, insisting that she must "wear special clothes for special occasions." Her older brother Toya Kinomoto watches over his sister while pretending that he is unaware of what is going on.