Kero

Cerberus (ケルベロス, Keruberosu) is a fictional character in Clamp's manga and anime series Cardcaptor Sakura. His name is more commonly known in its Greek version, Keroberos, which is also often shortened to Kero-chan or just Kero.

He is one of the two Guardians of the Clow Cards created by Clow Reed, along with Yue. Before his death, Clow appointed Kero as the one to select the potential candidate to be the next master of the cards, Cerberus himself, and his fellow guardian, Yue. After Sakura Kinomoto inadvertently releases the cards, Cerberus chooses her to be the candidate and teaches her the basics of capturing the cards.