A new day dawns in Wyndon as Ash wakes up at the Rose of the Rondelands hotel to find Goh having stayed up all night to study the data that Project Mew had sent for him so he can be ready for the next mission as soon as it happens. Ash decides to do some last-minute training with his team before the Masters Eight Tournament semifinals begin, but as soon as he calls for everyone to stop and compliments them, Dragonite tackles him in a very affectionate hug, causing both of them to slide through some bushes and end up right next to Cynthia and her Garchomp, who are also doing some last-minute preparations. As Goh and the rest of Ash's Pokémon join them, Cynthia demonstrates her usual pre-battle routine by having Garchomp fly around for a bit, giving her a back massage, and then having her fly around some more, with her going even faster now.
The group is approached by a young boy who introduces himself as Vic, along with his little sister Toria. Both of them are huge fans of Ash, Cynthia, and Leon, with Vic declaring that he wants to be able to use a move like Ash's Pikachu's 10,000,000 Volt Thunderbolt, choose Grookey as his starter Pokémon, and evolve it into a Rillaboom that can Gigantamax, just like Leon's Rillaboom. When Vic asks what Cynthia's first Pokémon was, Ash realizes he's never asked about it. Cynthia responds that Garchomp was her first partner, raised from a Gible that she hatched from an Egg as a child. This reminds Ash of how his Lucario also hatched from an Egg. Said Egg was very mysterious, as it refused to hatch and went from region to region, until Ash finally felt the Egg's Aura calling out to him, and it had hatched with him. Cynthia reveals that she had also heard of this mysterious Egg and figures it must've been fate for it to have wound up with Ash.
Vic thanks Ash and Cynthia of their stories and calls out to Toria, but before they can leave together, she gets distracted by a Gossifleur floating by and excitedly runs after it, forcing Vic to follow. Ash, Goh, and Cynthia head for Wyndon Stadium to watch the first semifinals match. No sooner have they arrived in front of the stadium and seen Leon entering the field on a giant screen, however, that they hear Vic nearby, having lost the sight of Toria. The group agrees to help find her and follows Vic just as the first semifinals match gets underway.
The group ends up finding Toria by following the sound of a Gossifleur singing, finding her watching said Gossifleur from a bush. The Gossifleur ends up evolving into an Eldegoss and flying away to scatter its seeds around Galar. Vic and Toria wave good-bye to it, before Vic suddenly remembers Leon's battle. The group rushes back to the stadium, where they're greeted by the shocking revelation that Diantha has already lost four Pokémon, while Leon has only lost one. Diantha's fifth Pokémon, Goodra, lands a super effective Fire Blast on Leon's Rillaboom, engulfing it in a giant fireball just as the group enters the stands. To Diantha's shock, Rillaboom manages to repel the flames by beating its drum before using Acrobatics, defeating Goodra and leaving Diantha with just one Pokémon against Leon's five. While Ash muses how he's never seen Diantha being backed into a corner like this, Diantha sends out Gardevoir as her final Pokémon. In the stands, Team Rocket gives a recap of the battle so far for the viewers of their broadcast, revealing that Rillaboom alone has taken down four of Diantha's Pokémon. While James and Meowth remain cheerful, Jessie stopped caring about the battle the instant Diantha's Gourgeist was defeated.
Diantha has Gardevoir attack with Shadow Ball. While Rillaboom manages to avoid the attack, its Knock Off is, in turn, dodged by Gardevoir, who follows up with Psychic to lift Rillaboom into the air and then slam it back down, finally taking the Drummer Pokémon out of action. Leon responds to this knockout by sending out Charizard. Seeing Leon's ace has entered the battle, Diantha immediately Mega Evolves Gardevoir, while Leon Gigantamaxes Charizard. Gardevoir attacks with a powerful Thunderbolt, which actually causes the giant Pokémon to stumble backwards. Leon launches his own attack in the form of Charizard's signature G-Max Wildfire, which engulfs Mega Gardevoir in a flaming vortex. In a maneuver that catches Leon off-guard, Gardevoir uses Psychic to redirect Charizard's G-Max Move right back at it, forcing him to use Max Airstream to counter it. Fueled by Diantha's unrelenting desire to never give up, Mega Gardevoir keeps pushing, causing G-Max Wildfire, Max Airstream, and Psychic to fuse together into a single devastating move. However, before it can make contact, Leon orders another G-Max Wildfire, which busts through the combination attack and strikes Gardevoir head-on. When the flames die down, Gardevoir collapses and is judged unable to battle, meaning that Leon has won and will be advancing to the finals.
In the stands, the group is excited by the battle they just witnessed, with Vic and Toria asking Ash and Cynthia to have a cool battle like this one with them once they become Pokémon Trainers, which they happily accept. After watching Leon and Diantha shake hands, Cynthia turns to look at Ash and Pikachu, whose faces are filled with determination as they prepare themselves to face Cynthia in their own semifinals match.