Kerberos, often referred to as Kero-chan by Sakura, is a fictional character from the anime series Cardcaptor Sakura. He is the Guardian Beast of the Seal, tasked with protecting the Clow Cards. Initially appearing in a small, plush-like form, Kero-chan is a playful and humorous character who loves sweets. However, when necessary, he transforms into his true form, a majestic lion-like creature. Kerberos serves as a guide and mentor to Sakura, helping her capture the Clow Cards and understand her magical abilities.