Dia (Alola)/History

Dia debuted in Battling the Beast Within!, where he encountered and  when they found themselves transported to his home world from an alternate Melemele Island by a   and the  of Ash's world. Ash and Pikachu were attacked by a Guzzlord, but Dia saved them using his friend. After introducing himself, he explained to Ash what had happened to his world and then had a battle against Ash, which Dia was able to win. Dia eventually took Ash to some ruins, which Ash recognized as the Pokémon School.

In Parallel Friendships!, Dia explained to Ash and Pikachu how his universe is different compared to his. He later explained that the reason Ash was unable to use a Z-Ring is because his Tapu Koko left the Alola region and all life was destroyed by Guzzlord. Since that time, Dia became disillusioned with Tapu Koko and believed that his efforts of stopping the were hopeless. However, all of that changed when he witnessed Ash and Pikachu's, which turned into a competitive battle against Zeraora. While Pikachu won the match, it reinvigorated Dia and Zeraora's ambitions.

The battle also attracted Guzzlord's attention, so Dia, Ash, Pikachu, and Zeraora were forced to put a new plan into action, luring Guzzlord to the Ultra Wormhole below the debris. When they attempted to ensnare the Ultra Beast in Pikachu's, Guzzlord fought back. Dia wanted to retreat, but Ash refused to give up. Just when they were about to be consumed by Guzzlord, Tapu Koko appeared and trapped it with its electricity. Tapu Koko reactivated Ash and Dia's Z-Rings, and together, they used their Z-Moves to push Guzzlord through the Ultra Wormhole. Dia thanked Ash for his help, and realized that it was time for Ash to return to his home world. He and Zeraora battled Ash again, which caused a dimensional rift to open up and allow Ash and Pikachu to return to their home world. The pair said goodbye to Dia and Zeraora and promised to battle them again one day before going their separate ways.

He reappeared during a flashback in SM140.