Gou is a Pokemon Trainer from Vermillion City in the Kanto Region. A chance encounter with the Mythical Pokemon Mew as a child ignites his desire to capture it. Gou generally struggles to make friends, but eventually meets Satoshi and quickly becomes close friends with him. Together, the two become research fellows at the Cerise Laboratory.
Initially hoping to make Mew his first Pokemon, the actions of a wild Scorbunny convince Gou to accept it as his first Pokemon. He then decides that he will catch every Pokemon while working his way up to Mew, due to the fact that Mew contains the DNA of every Pokemon. Gou would go on to capture many Pokemon over the course of the series.
His Scorbunny would eventually evolve into a Raboot and become disobedient over a previous argument with Gou over his inability to use the move Ember. In time, the two would reconcile, culminating in Raboot's evolution into Cinderace during the Darkest Day.
One day, Gou encountered a group of Pokemon Hunters attacking a Suicune. To rescue it, Gou captured the Legendary Pokemon in a Monster Ball and fled. While initially distrustful of Gou, after seeing how Gou desperately attempted to protect it, Suicune accepted Gou as its trainer, remaining as his Pokemon while roaming the world.
This legendary capture leads to Professor Oak offering Gou a recommendation to compete for a spot in Project Mew, a group whose ultimate goal was to capture Mew. Initially turning down the offer, a meeting with Shigeru would make him change his mind. After many tests, Goh would gain the necessary points needed to secure his spot in the team.
Project Mew would eventually locate Mew on Faraway Island in the Hoenn Region. Starting their expedition, they would come face-to-face with it deep inside the island. Ultimately, they were no match for Mew, but Gou managed to get his feelings through to it, even getting to hold it in his hand.
After returning from Project Mew, Gou decided to go on a journey across Kanto. At the same time, Satoshi had already decided to go on a journey around the world. Gou thanked Satoshi for everything before the two took separate paths.