Riolu was befriended by Kyle before moving to Almia (revealed in the Ranger Net mission Rescue Kidnapped Riolu!), and he seemed obsessed with Riolu beforehand. In the mission Rescue Kidnapped Riolu, Riolu should be saved from Team Dim Sun, as they will use it as weapon to restore them. It seems to have a connection with Kyle using Aura, since he used it to target to Team Dim Sun's hiding place when the lights went off. The Riolu is later captured by the player and can be sent to Pokémon Diamond, Pearl, or Platinum.
Diamond, Pearl, Platinum, HeartGold and SoulSilver
A Riolu can be transferred from Shadows of Almia to a Generation IV game and obtained through Mystery Gift. This male Riolu knows Aura Sphere (which, in the main series, cannot ordinarily be learned by Riolu) and has his Original Trainer registered as Kyle, the character he befriended in Shadows of Almia.
Riolu lives in the Lucario Kingdom. Its official title is Inheritor of the Aura, and it was specifically trained to learn Aura Sphere to defend the Kingdom. At some point, it was kidnapped by an evil organization and taken to a laboratory facility. It was freed in Pokémon Ranger and the Kidnapped Riolu! (Part 1) by another group of people led by a man with equally dubious motives. Riolu initially trusted its rescuers as they were wearing the Lucario Kingdom crest on their clothes, but it escaped after overhearing their conversation and learning their true motives.
Riolu fled into a nearby forest, where it encountered Ash and his friends. As Ash tried to approach Riolu, it attacked him with Aura Sphere. When it tried to attack Ash again, Kellyn, a Pokémon Ranger, blocked it using his Vatonage Styler. Riolu tried to escape, but the group pursued it, as did Hunter J, who had been commissioned by Riolu's earlier rescuers.
To try and gain Riolu's trust, Kellyn gave it a small pouch containing a small wooden Riolu made by Riolu's caretaker. However, Riolu was still unsure whether to trust the group or not. After Kellyn explained Riolu's situation, Ash was eager to help it get back home. While traveling down a stream, the group was attacked again, this time by a group of Sharpedo belonging to J's Henchmen, which destroyed their boat. J appeared and attempted to capture Riolu, but she missed and instead took the wooden carving floating downstream. Riolu swam after the figurine, but it was caught up in a strong current and nearly drowning. Ash managed to save Riolu and returned the wooden carving to it, which caused Riolu to begin trusting him. While trying to escape, they were spotted by J and her henchmen, and, in an attempt to lure Riolu out, J's Salamence set the surrounding forest on fire.
J confronted Ash and captured Riolu in Pokémon Ranger and the Kidnapped Riolu! (Part 2). Ash picked up the discarded wooden figurine and later sneaked aboard J's airship to rescue Riolu. J quickly ejected Ash from her aircraft and continued to the rendezvous point, where she delivered Riolu directly to her client. After realizing the strong Aura bond he shared with Riolu, Ash managed to track down Riolu, along with J and her client. Kellyn and Ash pursued the client through a cave and soon confronted him. The client dropped Riolu's glass case after his Aggron fell onto him. Ash quickly freed Riolu, who proceeded to use Aura Sphere to counter an incoming Hyper Beam. Pikachu used Volt Tackle to defeat the client, and Officer Jenny later made the final arrests. Afterwards, Riolu was reunited with its caretaker, and Ash returned the wooden carving to Riolu.
Personality and characteristics
Riolu is pure-hearted and sincere. It holds a deep respect for its homeland, the Lucario Kingdom, as evidenced by its attachment to a wooden carving made by its carer.
It was left traumatized and distrustful of humans after being constantly kidnapped by evil people. However, Riolu quickly struck up a friendship with Ash, as the two shared a similar Aura signature. This unique connection allowed the pair to communicate messages and images to one another, even when at a distance.