What If Ash was in Pokemon Horizons?

Me and Fuecoco's Song

Ash arrives in Alfornada and immediately rushes towards the gym. Of course stopping when a crowd starts to form around him and he has to take pictures and sign autographs.

???: Well, well well, seems like I'm not the only one drawing a crowd now.

Ash looks to see a grown woman with pink purplish hair, wearing a long dress and high heels, from what he's seen, it's none other than Tulip.

Ash: Tulip, I'm here to challenge you for my Terastal test!

Tulip: I'm not one to say no to a challenge, especially not one from The World Monarch. Meet me on the battlefield in five.

Five minutes later, Ash and Tulip take the field, Tulip sends out Espathra while Ash sends out Nymble. Espathra starts off with Shadow Ball, but Nymble dodges thanks to its small size and counters with Struggle Bug. Doing big damage, Nymble tries to charge in with Double Kick, but Espathra sends it flying with Psychic. Hurting it badly.

Ash: Nymble, return!

Ash returns Nymble to its Poke Ball and sends out his final Pokemon, Tauros. Tauros is still distrustful of Ash, only attacking what moves it wants to use, only occasionally obeying Ash. Together they're still able to defeat Espathra, though Tauros is weakened. Tulip then sends out her ace, Florges, and terastallizes it into a Psychic type. Tauros rushes in ready to use Assurance, but Tulip takes advantage of Tauros' rebellion and has Florges use a Psychic and Moonblast combo to take it out. Ash has no choice but to send out Nymble, still hurt from the previous battle.

Ash: I know you're hurt badly Nymble, but I know you can pull through!

Nymble jumps up trying to use Double Kick, but Florges uses petal blizzard to hit it away, then Psychic to beat Nymble down repeatedly.

Tulip: Seems like this battle is nearly over, Ketchum. It's been an honor.

Ash: I'm sorry, Nymble, I just thought that with your type and your spirit you'd pull through. But I put too much faith in you.

Nymble sees its trainer's defeated look, it remembers the terrible life it's had to live since it first hatched, constantly looked down upon and bullied. Stronger Pokémon beating on it for fun. Ash was the one person who supported it and now it's letting him down. It's proving everyone right, they can't be right. Nymble's supposed to win....

NYMBLE'S SUPPOSED TO WIN

Nymble lets out a large cry, so many years he spent in that forest, learning new moves to try and counter its bullies, but no matter what it'd never win. Now Ash was losing faith in it, not again... NOT AGAIN

Nymble gets absorbed into a bright light and evolves into Lokix

Ash: Woah! Who's that Pokemon?

Ash scans Lokix with his Rotom Phone

Rotom: Lokix, the Grasshopper Pokémon, a Bug and Dark type. When it decides to fight all out, it stands on its previously folded legs to enter Showdown Mode. It neutralizes its enemies in short order.

Ash: Awesome Lokix! You evolved! We're not out of this fight just yet!

Tulip: Well then! Florges, let's finish this in style!

Florges charges in with Psychic, but Lokix outspeeds with a new move, Lunge. Slamming right into Florges and then following up with Struggle Bug, wearing Florges. Ash then terastallizes Lokix into a Tera Bug type, boosting its Bug type moves. The two Pokemon exchange a few more moves before colliding with Lunge and Psychic respectively, but Lokix hits first, causing Florges to faint. Making Ash the winner.

Ash: You did it Lokix!

Ash and Pikachu run up to Lokix and hug it, Tulip returns Florges comes over to them and shakes Ash's hand

Tulip: Without a shadow of a doubt, Ash Ketchum, you passed your test, congratulations!

Ash sees his Rotom Phone, which shows that Tulip sent a stamp. So he says goodbye to Tulip and hops on a Flying Taxi back to Montenevera.

Ash arrives back in Montenevera and sees the concert stage again filled, with Roy and Rhyme at the battlefield, he reunited with Liko, Dot and Nemona. MC Sledge starts the battle, which Ryme initiates with a series of Overdrives. Fuecoco dodges all of them and uses Flamethrower as a counterattack. Toxtricity successfully blocks the attack with Boomburst. Ryme orders a Venoshock barrage, which Fuecoco dodges with Flame Charge before landing a hit and then attacking with Disarming Voice. That barely fazes Toxtricity, who lands an Overdrive on Fuecoco. Fuecoco stands back up, and Roy and Fuecoco start singing a new song while dodging and bouncing back from Toxtricity's attacks. The entire crowd joins in on the cheerful song as well, and the repeated Disarming Voices are starting to have an effect on Toxtricity. Fuecoco uses Flame Charge to land another hit, bouncing all around Toxtricity before landing another Disarming Voice and then a Stomping Tantrum, landing a super effective blow on its opponent and making the audience cheer loudly.

Ryme is impressed by Roy's performance, but refuses to give up, revealing her Tera Orb and Terastallizing Toxtricity into a Ghost type, Roy responds to by Terastallizing Fuecoco. Toxtricity attacks with a barrage of Terastal-boosted Hexes, all of which Fuecoco dodges while the crowd keeps singing and cheering. Fuecoco finally takes a hit from a close-range Hex, but his boosted Flamethrower pushes through and strikes Toxtricity, undoing its Terastallization and knocking it out. MC Sledge officially announces Roy as the winner of the match, Ash, Liko and Dot join him on stage, congratulating him.

Ash: Roy, man! That song strategy was awesome! What changed?

Roy: Well, I thought Fuecoco and I were singing to get stronger, but we sang together to show off our feelings.

Liko: Then everyone singing together, sharing their own feelings must've helped Fuecoco then!

Roy: Right on the money!

Ryme walks up to them and compliments Roy on figuring out the true purpose of singing. She then takes out her Rotom Phone, and proudly announces that Roy has passed his test, sending him a stamp. Roy's friends all celebrate with him and turn their attention towards Liko's upcoming test and start heading for Glaseado Mountain.