Card Captor Sakura
Overview:
The story is about a 10 year old girl named Sakura Kinomoto (Sakura Avalon in the WB adaptation, "Card Captors".) who accidently found a book call "The Clow" in her father's library. The book originally contains some magic cards call "Clow Cards" but, when she opened the book, several cards escaped. The cards had a guardian named Kerberos, who had fallen asleep, therefore allowing the cards to escape.
Kerberos then choses Sakura to be the "card captor" and capture all the cards back before they bring destruction. This is when Sakura's adventure begins.