Pokemon Season 11 - Episode 534 – Pokémon Ranger and the Kidnapped Riolu! Part One

On their travels, Ash and his friends meet up with another Pokémon Ranger—Kellyn—and a Riolu. It turns out that Hunter J is after Riolu, due to its ability to use Aura Sphere before evolving. Ash and Riolu start to bond with their shared Aura, but J is insistent on getting it.