You’ll be able to find six Pet Pals volumes on your travels, each giving Rinoa extra limit breaks.

Pet Pals Vol 1 – Train to Timber – Angelo Strike
Pet Pals Vol 2 – Rinoa’s Bed, during the train mission – Angelo Recover
Pet Pals Vol 3 – Buy at Timber the Pet Shop – Invincible Moon
Pet Pals Vol 4 – Buy at Timber the Pet Shop – Angelo Reverse
Pet Pals Vol 5 – Buy at Timber the Pet Shop – Angelo Search
Pet Pals Vol 6 – Buy at Timber the Pet Shop – Wishing Star