In the Bagon

Ash confidently strode down Route 1, the new Normalium Z held firmly in his Z ring.
"Aw yeah, first trial complete! What's next: Photo Safari in Ten Carat Hill? Climbing to the top of a haunted tower? Ooh- how about..."
Ilima laughed before cutting Ash off.
"Easy, Ash. Next is the Grand Trial against Kahuna Hala."
"Oh yeah, you did mention that. So what is this grand trial anyway?"
"The Grand Trial is the final trial a trainer undergoes on an island of the Alola region. It's actually quite similar to the Gym Battles you are familiar with, where you battle a strong trainer in order to receive a reward, in this case a Z Crystal. Here in Alola, the battle is against the Kahuna of the island. Once you've defeated them, you are recognized as the strongest trainer of the island."
Ash's eyes lit up in excitement.
"Really?"
"Well, until someone else beats Hala, then not so much. But you still get a Z Crystal."
Ash face faulted at this, but quickly shook it off.
"Well, let's get moving! The sooner we get back to Iki Town, the sooner I get my second Z Crystal."
"Pika!"
"HELP!"
Ash and Ilima turned to find Lillie struggling to free her bag from the grip of a wild Vullaby.
"Go away! Shoo!"
"By!"
Before Ash or Ilima could send out a Pokémon to help, a large burst of fire struck Vullaby from the side, forcing it to release Lillie's bag. When the flames died down, a wild Bagon, was snorting furiously. Realizing it was outclassed, the diapered Pokémon flew away, Bagon futilely trying to jump and grab it.
"Gon, Bagon!"
Ash and Ilima ran over to Lillie, who was trying to catch her breath.
"You alright, Lillie?"
Lillie straightened herself, nodding and smiling.
"Yes, thanks to that Bagon. Oh, I don't know what I would do if I lost Nebby."
"Pew! Pew!"
The Bagon continued to futilely jump for a few minutes before giving up and sulking over to some rocks by the cliffside. The three watched him.
"Man, that Bagon sure does seem upset. It must really hate Vullaby."
"I wonder why?"
"Perhaps I can be of service!"
Ash's Rotomdex flew out and over to the Bagon.
"Hey there big guy. Why the long face?"
"Bagon."
"Aw, come on. Tell Rotom what's wrong."
The Bagon sighed, before telling its story.
"Gon, Bagon."
"What? Really?"
"Bagon!"
"HE DID WHAT!"
"Bagon, Gon Bagon!"
"Come here, big guy. Rotom's got ya!"
With that the two hugged, tears flying out like crazy. Ash, Ilima, and Lillie just stared awkwardly.
"Uh, Rotom? Mind filling us in?"
Sniffling, Rotom and Bagon shuffled over to them.
"Oh Ash, I shall try my best to recount this poor soul's tragic tale. You see, his trainer abandoned him because he didn't want to wait so long for a Salamence, called him weak
and left him to suffer on his own. For years Bagon has wanted to fly and prove his trainer wrong, but no matter how hard he may try he could never reach his goal. Oh poor Bagon, my heart aches for thee."
Ash and his friends stared in shock for a minute.
"Oh man, that's terrible."
"Indeed. Anyone who would abandon their Pokémon has no right to call themselves a trainer."
After a second, Ash smiled and bent down to Bagon's height.
"Well, what do you say you and me prove him wrong together? I promise I'll have you flying in no time at all."
Bagon's eyes widened, taking in the offer for a second. After a moment, it nodded confidently.
"Gon, Bagon!"
"Alright. Welcome to the team, Bagon!"
Ash took out an empty Poke Ball from his pocket and lightly tapped Bagon on the head, absorbing it in. It only shook once before dinging, signaling that it was caught.
"Alright! I caught a Bagon!"
"Pika Pika!"
Afterwards, Ash and his friends continued along Route 3 towards Iki Town.
They reached Iki Town by sunset, tired but confident. Hala was at the town entrance with Professor Kukui, and waved to them as they climbed the steps.
"Hey there, guys! Ilima told me you beat his trial Ash! Whoo, that means you're ready for Hala's Grand Trial, Ash! You ready?"
To everyone's surprise, Ash shook his head no.
"Sorry, but my team and I have some training to do. Got to be ready you know?"
Hala gave a hearty laugh.
"Ha Ha, I agree 100%! When you are ready for my Grand Trial, come see me at my house. I shall be awaiting your challenge."
"Can't wait for it, Hala."
With that the groups departed, Hala and Kukui heading off for Route 1 while Ash and his friends heading to the Pokémon center for the night.
"You ready for our next battle, Pikachu!"
"Pika!"
"Yeah, me too. Look out, Hala. Ash is coming for you!"