Vermilion Forest first appeared when Ash and Goh, with their partners Pikachu and Scorbunny, went with the goal of capturing lots of different Wild Pokémon. After failing to catch a Pidgey, Pidgeotto, Diglett, and Dugtrio, Goh decided to focus on catching the twelve Kanto Bug-types, as they’re easier to capture and all twelve could be found in the forest.
After starting his quest, Goh quickly captured a Caterpie, Metapod, Venomoth, Paras, and Parasect. After spotting a Butterfree, he and Ash chased it into a colorful field. The Butterfree flew into a tree, so Goh climbed after it, while Ash went to investigate a nearby noise. Goh captured the Butterfree with the hell of Scorbunny, but before long hey found themselves attacked by a wild Pinsir. Pinsir managed to trap Ash and Pikachu with it’s Rock Tomb, leaving Goh and Scorbunny petrified. Goh, in his peril, started to throw random objects at it to defend himself, eventually accidentally throwing a Poké Ball and capturing it.
Afterwards, Ash and Goh temporarily split up as both Pikachu and Scorbunny heard different Pokémon and headed in opposite directions. When Goh found what Scorbunny was looking for, it turned out to be a Scyther. Goh attempted to capture it, but was easily defeated and Scyther managed to escape despite being cornered. Goh, however, was not deterred, saying he would capture it next time, and headed off to capture more Pokémon. He quickly encountered a Weedle and Kakuna, capturing both of them. However, he angered a group of Beedrill in the process, which began to chase after him. Goh reunited with Ash, and they both began to run from the Beedrill in fear, with Ash eventually having Pikachu use Electroweb to stop them. One Beedrill managed to avoid the attack, and Goh captured it, assuming that it was the strongest and fastest in the group.
With just two remaining Pokémon left on his list, Goh set out to encounter a Venonat, which he soon did. The Venonat managed to escape his first Poké Ball, and Ash recommended battling it, but Goh refused, saying that his method of simply throwing Poké Balls was ultimately faster. However, Scorbunny took the initiative and attacked first, so Goh complied and battled it. He and Scorbunny managed to weaken it enough to be captured, but not without being hit by Venonat’s Poison Powder. Goh brought Scorbunny back to the Pokémon Center and apologized for making it battle despite being poisoned, but Scorbunny forgave him.
Ash and Goh returned to Vermilion Forest afterwards, and decided to have a competition to see who could capture the Scyther Goh found earlier first. Eventually, Goh managed to find it before Ash could, and after another failed attempt at not weakening it and only having a single Poké Ball left, Goh decided he would have to battle and weaken it. Ash later caught up, but wasn’t upset that Goh found it first, and cheered Goh on as he battled. Scyther put up a brutal fight, but after a hard and difficult battle, Goh managed to weaken it enough to be captured. After capturing Scyther, Ash and Goh left the forest.
The two boys later returned to the forest with their new friend, Koromi, who was looking for a Pinsir, and her partner, Heracross (along with this, Goh’s Scorbunny had since evolved into Raboot and Goh had added a Sobble to his team). Goh also brought his own Pinsir, which he had captured here as well, along with him. Goh’s Pinsir is extremely shy, and was afraid of both Koromi and her Heracross. Ash and Goh had brought Koromi to the forest because they knew they could be found around here. They searched through the forest, looking in trees and bushes, but they ended up having no luck. However, Goh’s Pinsir started to become interested in Koromi’s Heracross after seeing how strong it was. Disappointed but not ready to give up, Koromi decided to make a special batch of honey that would be irresistible to wild Pokémon. After she was done, they set their lures around the forest.
During this time, Team Rocket members Jessie, James, Meowth, and Wobbuffet were searching the forest for Pokémon to steal, but were too starving to actually do anything due to a Morpeko that had followed them from the Galar Region eating all of their food. They eventually found some of Koromi’s honey, which completely revitalized them. In their desperation for food, they ate almost every single plate of honey the group had set out. When Team Rocket was finally discovered, they summoned the Rocket Prize Master, receiving a Scolipede and a Drapion, and captured Ash, Koromi, Pikachu, Raboot, and Sobble in a net, leaving just Goh, his Pinsir, and Koromi’s Heracross to defend themselves. The Scolipede and Drapion ended up getting distracted by the honey, which also left Team Rocket to fight for themselves. Goh attempted to get Pinsir to battle, but she refused. Heracross decided to step up and fight with Goh. They easily took out Meowth in just two attacks. When Jessie and Wobbuffet attempted to capture Pinsir, Heracross easily disposed of them, and Pinsir developed a crush on Heracross. Afterwards, they sent Team Rocket blasting off, and a wild Pinsir finally appeared, but since Koromi was still captured, she couldn’t capture it. Seeing that Koromi was still captured, Goh caught the Pinsir before it could get away. Once Goh freed everyone from the net, Koromi told Goh that he should trade her that Pinsir for her Heracross, since his other Pinsir was in love with it. Koromi also revealed that she had five more Heracross, so she was okay with parting ways with one. Goh agreed, and everyone left to go to the Pokémon Center to make the trade official.