Another possibility is that the shiny Riolu has some special powers that Ash discovers. They could be related to a hidden legend in the Pokemon world. Ash and the Riolu then have to protect this secret from those who would use it for evil. They might travel to ancient ruins and encounter other mysterious Pokemon on this journey.
The potential for different storylines. As I mentioned before, they could be on an adventure, training, or uncovering secrets. All these storylines can keep the readers engaged. For example, if they are on an adventure, the readers will be eager to know what new places they will visit and what Pokemon they will meet. If it's about training, we can see the Riolu grow and develop new abilities, which is always exciting in the Pokemon universe.
The fanfiction could revolve around Ash and Riolu's bond. Since Riolu can sense auras, it might be able to sense Ash's strong will and determination. They could go on an adventure to discover more about Riolu's species and its hidden powers. Along the way, they meet other trainers and Pokémon, and Riolu grows stronger with Ash's guidance.
In another plot, Riolu could be a Pokémon that has been abandoned by its previous trainer. Ash stumbles upon it while on his journey. At first, Riolu is very distrustful of humans, but Ash shows it kindness and patience. Through Ash's training methods and the bond he forms with his other Pokémon, Riolu slowly warms up to him and allows itself to be caught.
Well, the plot could involve Ash's transformation into Riolu being a result of some magical or scientific experiment gone wrong. Maybe he has to adapt to his new form and learn to use Riolu's abilities like Aura Sphere. He might also struggle with being recognized by his friends at first.
Well, perhaps Ash could be magically transformed into a Riolu. He might then struggle to adapt to his new form. For example, he would have to learn to use Riolu's unique moves like Force Palm in a completely different way compared to using his Pokémon attacks as a human. He could also face challenges in communicating with his old Pokémon friends as a Riolu.
Well, it could be about Ash finding a lost Riolu in the forest. Ash decides to take care of Riolu and train it. They go on adventures together, facing different Pokemon battles. Riolu could grow stronger under Ash's guidance and they might aim to win a big Pokemon tournament.
One possible plot could be that Riolu is being chased by some bad guys who want to use its power. Ash rescues Riolu and they team up. As they journey, Riolu learns from Ash's kindness and determination. They enter Pokémon battles together, and Riolu's unique fighting style combined with Ash's strategies help them win. Also, their relationship could grow deeper, with Riolu becoming one of Ash's closest Pokémon companions.
Perhaps the fanfiction could have a plot where Ash discovers a Riolu with some special abilities. He has to protect Riolu from those who want to use its powers for bad. This could lead to an adventure filled with battles and new friendships for Ash and Riolu. It might also explore the bond between Ash and Riolu as they grow together. Ash could learn new training techniques from Riolu's unique skills, and Riolu could learn about trust and friendship from Ash. There could be a big showdown at the end against an evil organization that wants to capture Riolu.
The plot could involve Ash starting his journey in a unique way. Since he has a shiny Charmander, it might attract the attention of Team Rocket more than usual. They could constantly try to steal it, creating many action - packed chase scenes. Ash would have to train his Charmander to be stronger to fend off these threats. Along the way, he could meet other trainers with rare Pokémon who are both friends and rivals, all while aiming for Pokémon League championships.
One possible plot could be that Ash's shiny Pikachu is targeted by an evil organization because of its rarity. Ash has to protect it while also trying to figure out why the organization wants it so badly.