His Pokémon's reactions could vary greatly. For example, his more sensitive Pokémon like Bulbasaur might be a bit worried about Ash at first. It could sense that something is different but not fully understand what. However, as Ash starts to use his Aura Guardian powers for good, like healing injured Pokémon or fending off stronger opponents, they would all gradually grow to trust this new aspect of Ash. And they might even start to develop their own ways of interacting with Ash's aura, like using it as an extra source of energy during tough battles.
Some of his Pokémon might sense the change in Ash immediately. Pikachu, being his closest partner, could be both curious and a bit protective. It might stay closer to Ash during battles, as if it knows Ash has a new power to draw from. Other Pokémon like Charizard might be a bit more aloof at first, but as they see the benefits of Ash's aura powers in battles and in protecting them, they would come to accept and rely on it.
Well, Pikachu, being so in tune with Ash, would likely be the first to pick up on Ash's new role as an Aura Guardian. It might nudge Ash more often, as if trying to communicate its awareness. His Flying - type Pokémon like Pidgeot could feel a new sense of security when flying with Ash, as if his aura was providing an extra layer of protection. His Water - type Pokémon might notice that Ash can now sense things in the water better, like hidden currents or the presence of rare Pokémon. Overall, his Pokémon would adapt to this new Ash, some more quickly than others, but all would ultimately see it as an advantage in their adventures together.
At first, his Pokémon would be startled. They've always known Ash as a human. But then, they would start to adapt. Some Pokémon, like Squirtle, might try to play with Ash in his new form, thinking it's a new kind of game. However, his more loyal Pokémon, like Greninja, would be determined to find a way to turn Ash back. Greninja might use its special bond with Ash to try and communicate with him on a deeper level in this new form, to understand what happened and how to reverse it.
One possible plot could be that Ash discovers his hidden ability to be an Aura Guardian gradually. Maybe he starts having strange dreams about it at first. Then, in a battle, he unconsciously taps into his aura power to save his Pokémon. This new power would lead him on a journey to understand more about the Aura Guardians, their history and his place among them.
Some of his Pokémon might be very confused and sad. Pokémon like Pikachu, who has been with Ash for a long time, would probably miss the adventures and battles they had together. Pikachu might try to cheer Ash up and convince him to change his mind.
Some of his Pokémon like Pikachu might be very protective. Pikachu would stay close to Ash at all times, being extra vigilant in case any danger comes while Ash is in this new form. It would also be curious and might try to play with Ash's new fairy features, like his wings if he has any.
His other Pokémon like Charizard would be completely bewildered. Charizard might initially think that this Eevee is just some random Pokémon near its territory. But when it senses something familiar about the Eevee, it would be hesitant and curious. It could try to communicate in its own way, like using small bursts of fire to get the Eevee's (Ash's) attention. The Pokémon that Ash has a closer bond with would be more determined to figure out what's going on and how to help him.
His other Pokémon like Bulbasaur and Charmander would also be startled. They might gather around Ash - Zoroark and sniff him out to make sure it's still him. They could be a bit hesitant to follow his commands at first because they're not used to his new form. However, as they see that Ash's spirit is still there, they would gradually start to trust and follow him again, and they would work together to figure out how to turn him back.
His Pokémon would probably be very confused at first. Pikachu, for example, might try to zap Ash back to his senses if he starts acting like a Team Rocket member. They would likely sense that something is wrong with Ash and would do their best to get him away from Team Rocket's influence.
Some of his Pokémon might be confused. Pokémon like Pikachu, who has a very close bond with Ash, would initially be in shock. Pikachu would likely try to understand why Ash is doing what he's doing and might even try to stop him at first.
One great aspect of Aura Guardian Ash fanfiction could be the exploration of Ash's latent aura powers. Maybe in these stories, Ash discovers he has a much deeper connection to the aura realm than he ever knew. This could lead to him having new abilities and forming unique bonds with Pokémon that are also attuned to the aura.
If Ash was secretly a Pokémon, trainers might view Pokémon in a whole new light. They would see that Pokémon could be more like them, with complex emotions and motives. Also, Ash's relationships with other Pokémon and trainers would be re - evaluated. His Pokémon friends might see him as an equal rather than just a trainer.