Kero has taught Sakura almost everything she knows about Clow cards since he was released from the book with the cards by Sakura. To return to his original form of the Guardian Beast, two cards must be captured. (The Firey and Earthy)
Kero's appearence is similar to a lion-like teddy bear with wings, and he uses this to pretend he is a toy, keeping Sakura away from suspision. He always argues with Li and Meilin about how good Sakura is at CardCaptoring.
In Season Two, Kero continues to hang around enjoying the things he loves. However, he needs to be able to protect and guide Sakura more than ever now that she faces the duty of transforming all of the Clow Cards into Star Cards.
This shouldn't be much trouble for him, as he can now become Keroberos. However, it seems he must also be sealed with another guardian beast name Spinner.
