Having just caught Scorbunny, Goh is keen to catch more Pokémon and fill the Pokédex. Ash suggests they go right now, so the boys make their way over to Vermilion Forest. Goh is fully stocked with Poké Balls. Pikachu leads them to a Pidgey nesting in a tree. Goh eagerly tosses a Poké Ball its way, only for it to rebound off of a tree branch instead. Pidgey is also alerted to their presence and blows them away with Gust. Ash advises Goh to be more careful next time, though just as rash as before, Scorbunny rushes over to a nearby Pidgeotto. However, Pidgeotto hears them coming and flies off into the distance. Just as Goh asks Scorbunny to be calmer, it starts chasing a Diglett around. Suddenly a Dugtrio bursts from the ground, carrying Goh off while the others follow after him. Goh sees his chance to catch it, but Dugtrio returns underground, causing Goh to crash into Scorbunny headfirst.
Scorbunny's ears twitch again, leading Goh and Ash directly to a leaf-munching Caterpie. Trying a more careful approach, Goh and Scorbunny crawl towards their target before catching Caterpie. Goh then asks the Pokédex about what other Pokémon he can catch in the area, and he sets his target of completing the Caterpie evolutionary line. However, the search isn't going so well, until they hear a rustling in a tree. Ash and Goh kick the trunk, though a tree branch falls onto Goh. Scorbunny and Pikachu follow suit, causing a Metapod to land on Ash. Goh quickly throws a Poké Ball and catches the Metapod for himself. Goh soon adds a Venomoth, a Paras, and a Parasect to his collection. A Butterfree then flies past before resting in a nearby tree, and Goh gives chase. After a failed throw due to height, Ash gives Goh a helpful hoist. Goh, however, fumbles the Poké Ball, though Scorbunny kicks it and successfully captures Butterfree.
Meanwhile, Ash and Pikachu go over to inspect a rustling shrub but are startled to find an aggressive Pinsir who attacks them with its gnashing horns. Pikachu strikes it with a Quick Attack, though Pinsir traps him and Ash inside a Rock Tomb. Pinsir then turns its attention to dealing with Goh. Goh, startling, throws items to keep Pinsir away, and unintentionally captures it in the process. Soon, Goh finds another dangerous Pokémon, a Scyther. He tries throwing a Poké Ball at it, but Scyther slaps it away with its sharp scythes. It follows on with Air Slash, sending Goh and Scorbunny blasting off. After landing, Goh sees that Scyther has fled, so he decides to turn his attention to catching the Weedle evolutionary line.
Scorbunny soon spots an oblivious Weedle in a tree, and Goh lands the catch with a single throw. Goh then finds a horde of Kakuna dangling from the trees, and catches one for himself. As he goes to retrieve his catch, a swarm of Beedrill readies their stingers to attack. Goh and Scorbunny rush over a hill, warning Ash and Pikachu of the impending danger, as the Beedrill fly after them. Pikachu uses an Electroweb to trap their pursuers; however, one Beedrill avoids the trap. Goh sees this Beedrill as the strongest and throws out a Poké Ball to make another successful catch. Goh is thrilled with the day’s result, but with two remaining, he hopes to complete his Kanto Bug-type collection. He informs Ash that he spotted a Scyther earlier, though Venonat may be a tougher find as it is nocturnal.
On a hunch, Goh inspects a tree hollow and screams out as he comes face to face with a Venonat. The Insect Pokémon bounces out of its hideaway, so Goh throws a Ball at it. However, Venonat doesn't get caught as easily as the others. Instead, Ash suggests Goh battle it first. Goh outright refuses and claims that throwing a Poké Ball is faster. However, Scorbunny leaps into action, determined to battle Venonat. Goh spurs Scorbunny on and orders a Quick Attack. Venonat replies with Poison Powder, which poisons Scorbunny. Goh orders a Double Kick before making his catch. Goh turns his attention to getting Scorbunny some treatment, so the boys rush towards the nearest Pokémon Center. Soon enough Nurse Joy and Chansey discharge Scorbunny with a clean bill of health. Goh apologizes for letting his Pokémon get injured, though Scorbunny is just as enthusiastic to help Goh in his catching quest as before.
Returning to the forest, Ash and Goh split up to find Scyther. Scorbunny is the one to find Scyther. Goh tries another Poké Ball, but Scyther once again slaps it away. With one Poké Ball remaining, Goh decides to settle things with a battle. Scyther dodges Scorbunny's Quick Attack and attempts to strike it with an Air Slash, which misses. Ash and Pikachu arrive on the scene just as a Double Kick from Scorbunny fails to its mark. Scyther knocks Scorbunny to the ground with a Slash attack. Goh calls for another Quick Attack, with Scorbunny delivering a successful kick on Scyther. Goh then throws out his Ball, landing the catch. Goh is ecstatic to have caught all twelve of Kanto's Bug Pokémon. He and Scorbunny exchange a high-five to celebrate.
The next morning, Chloe and her father, Professor Cerise, notice that the boys haven't woken up yet for breakfast. When they hear laughter, they find Ash and Goh swarmed by all of the Bug Pokémon in their bedroom. Cerise is thrilled by the interactions, before unveiling his purpose-built greenhouse ecosystem, the Cerise Park, to house all of the Pokémon. Chloe questions why Goh didn’t make Mew his first catch. Goh smugly replies that he will catch every Pokémon he can, hoping to get closer to finally fulfilling his long-term ambition of catching Mew. Ash admits his dream is to become a Pokémon Master. Chloe and Goh are confused, but Ash explains that it is much more than being the world's greatest Trainer. Even so, Goh and Ash spur each other on to achieve their seemingly impossible dreams.