"You fell from the sky?"

"Yeah," Ash confirmed. "It was kind of weird, I don't remember exactly what I was doing before that, but, uh… here I am!"

He rummaged in his pocket, and brought out his phone. "Hey, where are we, exactly?"

"What's that?" the man asked, before Rotom could respond.

"Huh?" Ash said. "Oh, this is my Rotom Phone. I got them earlier this year."

"Attention," Rotom said. "I cannot find a compatible network."

"Pika?" Pikachu asked. "Pika-chuu, Pikapi."

"Huh, maybe," Ash replied. "Where is this place, anyway?"

"That's amazing," the man said. "Some kind of talking device?"

He looked at Pikachu, a little warily. "And – are you sure you're all right with that Pokémon so close to you? Not even in a Pokéball?"

"Hey, Pikachu doesn't like Pokéballs!" Ash replied. "And he's my best friend."

"Chaaa!" Pikachu agreed, ears twitching. "Chuu, Pika?"

"Like I said," Ash resumed. "Where are we, exactly? I did fall out of the sky so I guess I probably got lost again."

"...again?" the man said, then shook his head. "Oh, sorry – this is Hisui."

"Never heard of it," Ash admitted. "But, I guess that's not really unusual for me."

Rotom went bwip.

"You have a new message," they said. "Message is from: The Alpha Pokémon. It says: Seek Out All Pokémon."

"Thanks, Rotom!" Ash told them. "I guess that must be why I'm here!"

"The Alpha Pokémon," the man repeated to himself. "I've never heard of that Pokémon… is it another name for Unown?"

"No, Unown is something else," Ash replied. "Though I guess Unown could have been involved somehow…"

He scratched his head. "Well, I guess I should try and find how to get home somehow, and if all I've got to go on is instructions to seek out all Pokémon, I guess it's time to do that! Looks like we're going to be doing things Goh-style, huh, Pikachu?"

"Ka-chuuu," Pikachu sniffed.

"Hey, I didn't mean all the ways!" Ash defended himself, chuckling. "Just about, you know, catching more Pokémon. Maybe we'll make some new friends, too!"

"You're certainly an interesting young man," the man admitted. "Well, if you are going to try and seek out all Pokémon, I don't suppose you'd be willing to help me out in gathering some observations? I'm trying to create a kind of encyclopedia of all the Pokémon in Hisui based on first-hand observations, you see."

Ash mulled that over, then nodded. "Sure! My friend Tracey's a Pokémon Watcher, so I know how to do that!"

"Pika-pika, Pikapi," Pikachu said, sniffing.

"Well, I know the theory, anyway," Ash amended. "You know, follow Pokémon around and make drawings of them! Actually, uh, do photos count?"

The man chuckled. "I suppose they do… and my name's Professor Laventon. It's nice to meet you."

"Ash Ketchum!" Ash replied, holding out his hand.

Then a white and green blur knocked him over.

"Ash!" Professor Laventon said, then stopped at the sight of the Pokémon who'd ended up on top of Ash. "That's… I've never seen that Pokémon before."

"Hi, there," Ash said, completely unfazed by being bowled over by a Pokémon. "The last Shaymin I saw was my friend Mallow's… I guess there must be Gracidea not far from here, right?"

"Shaay-min!" the Shaymin said, tilting their head. "Miin?"

"Yeah, she didn't stay with Mallow forever, but she did battle for Mallow in the Manalo Conference," Ash explained. "Actually, uh, does this place have any gyms?"

Laventon looked perplexed. "Are you not… worried? That's an unknown Pokémon and it just knocked you over!"

"Not the first time it's happened!" Ash replied. "Not the first time it's happened with a Shaymin, either."

Laventon absorbed that, then got around to the question Ash had asked.

"...what's a gym?"

Ash exchanged a glance with Pikachu.

"Okay, we're a long way from home," he said.

"Pikaaa," Pikachu agreed, ears flat.

AN:

This probably comes some time before the Arceus Chronicles special, but apart from that the only real guideline is that it's somewhere in Journeys.