It’s time for research fellows Ash and Goh to explore the Galar region’s Wild Area, known for Dynamax—a phenomenon in which Pokémon can grow to many times their normal size. Our heroes’ train ride there is filled with anticipation…and that mischievous Scorbunny has secretly come along for the ride.
They come across a Snorlax who suddenly grows to gigantic size and sprawls across a railroad crossing, still fast asleep! As the train speeds toward them, Scorbunny shows up to help. Working together, they get the Dynamax Snorlax out of the way in the nick of time—and Scorbunny convinces Goh to become its Trainer!
Aboard a train to the Wild Area, Scorbunny stares out into the countryside before searching for Goh. It soon locates Goh and Ash eating in a dining car, but the boys are too deep in conversation to notice Scorbunny leaping up to get their attention. Scorbunny walks off in frustration and takes some food off a nearby cart. After a bite, it kicks the fruit away; however, it strikes a passing waiter who loses his balance and accidentally knocks the tray of food over.
The train stops at a station, where Goh and Ash get off. Scorbunny wakes up but is too weary to hop off. It panics as soon as it spots Goh on the platform, but the doors seal shut and the train takes off again. Scorbunny eventually locates an open window and leaps to freedom. It readies itself before running on the tracks back towards the Wild Area station. Meanwhile, Goh approaches a concierge for more information about the Dynamax phenomena, and the concierge directs them to follow the red lights. After some exploration and snapshots, Ash and Goh soon come across a set of crossing signals. Ash considers if these lights are the ones described by the station concierge earlier, but Goh dismisses the idea.
They leap over the tracks and rush towards a napping Snorlax. Goh pulls out his Rotom Phone and begins recording details on Snorlax. After analyzing Snorlax, the boys are left disappointed by the lack of interaction. Meanwhile, Scorbunny is thrilled to finally see Goh again and rushes over to greet him. However, Ash and Goh are too occupied by Snorlax. Scorbunny responds by kicking a stone, which ricochets off Ash's head and knocks a Sitrus Berry out of a tree and directly into the sleeping Snorlax's mouth. Snorlax chews the fruit and spits out the seed before returning to its slumber. Ash tries to nurse his sore head and as he turns to Goh he spots Scorbunny. Ash and Goh instantly recognize it as the very same Scorbunny they met yesterday, and are pleased to see that it has cleaned itself up. As Scorbunny affirms that it has been following, Ash suggests it might want to join Goh's team. Goh, however, apologizes to Scorbunny, admitting that he wants his starter Pokémon to be Mew. Scorbunny is disappointed and bows its head in response.
Suddenly, mysterious red lights appear and float towards Snorlax. A burst of energy then engulfs Snorlax, causing it to swell to enormous proportions before it emerges in its Gigantamax form. Goh is quick to point out that Snorlax is now blocking the train tracks, adding that a train is due to pass through in the next eight minutes. Ash has Pikachu use Thunderbolt, but Snorlax is only mildly disturbed and fires off a Hyper Beam in its sleep. Ash resorts to yelling but quickly shelves that idea when Goh points out the giant berry growing from the tree now sprouting from Snorlax. Goh figures that Snorlax will wake up if they feed it the berry. Ash is all in and begins to climb on Snorlax and onto its tree. Goh clambers up with some struggle, before ordering Ash to drop the berry. However, Pikachu's Iron Tail fails to cut through the thick stem and now only four minutes remain before the train arrives. Ash leaps onto the berry, and using his added weight he swings the berry as Pikachu attacks the stem with a flurry of Iron Tails. The berry drops as planned, but gets caught up in the growing shrubs. Goh tries to push the berry, but his might isn’t enough. As the crossing signals sound, the situation grows tense. Luckily, Scorbunny leaps in to help. Goh notices Scorbunny's feet digging into the ground as it tries to push the berry. He recalls Scrobunny's powerful kicks and orders it to use Double Kick. Scorbunny follows suit and the force is enough to cause the berry to rolls towards Snorlax's mouth. Snorlax leaps upwards to grab the berry, and as it plummets, the shockwave stops the approaching train.
Goh realizes Snorlax must have also swallowed Scorbunny, but he is reunited with his friend after Snorlax returns to its usual form. Goh thanks Scorbunny for its help, pointing out that its Double Kick saved the train. Scorbunny is overwhelmed by the compliments, though prepares to walk off, remembering what Goh said earlier. Goh looks on for a moment but asks Scorbunny to wait. Scorbunny turns around and is pleasantly surprised when Goh announces that it will be his first Pokémon. Goh throws a Poké Ball, but the curveball misses its mark. Scorbunny resorts to kicking the ball to complete the capture. After the ball stops rocking, Ash affirms that Goh now has Scorbunny. The Rotom Phone's Pokédex function updates its systems on Scorbunny, making Goh realize he has finally caught his first Pokémon. Goh calls out his new recruit and exchanges a high-five to commemorate the beginnings of a new friendship.
Ash and Goh later return to the Cerise Laboratory. They update Professor Cerise on their adventures with a Gigantamax Snorlax. Yamper runs in and starts barking at Scorbunny, though Pikachu quickly settles the situation. Scorbunny is left feeling jealous of the Electric duo's playful friendship, so it returns to Goh for comfort. Cerise is confused to see Scorbunny. Goh grins as he affirms that Scorbunny is his first Pokémon.