"Herein lie the Clow Cards—if their seal is broken, disaster shall befall this world..."

Sakura Kinomoto is an energetic and sweet 10-year-old girl attending Tomoeda Elementary School. One day not long after entering the fourth grade, Sakura finds a mysterious book titled The Clow hidden within her father's bookshelves. Upon opening it, a small, winged creature with an Osakan accent comes out of the book and introduces itself as Keroberos, the Creature of the Seal who guards magical cards known as the Clow Cards and keeps them from escaping the book.

Unfortunately for the plushy guardian, it seems that the Clow Cards have already escaped—and now Sakura is tasked with capturing them before the cards unleash their powers and cause havoc all over Tomoeda! With the support of the tiny guardian who she nicknames "Kero" and her best friend, Tomoyo Daidouji, Sakura must wield a magical bird-shaped key and use her new powers as the Cardcaptor to maintain peace and ensure that everything is alright.