Kerochan is the guardian beast of the Clow Book.His symbol is ˇySunˇz.He can speaks any language and he is very vain.
He guides Sakura in her quest to recover the Clow Cards.And when Sakura recover one Clow Card,his power will be regained.
After all the Clow Card returned to the Clow Book. Kerochan still stay here to help Sakura(Sakura had become his master). Now he can change his deportment freely.