Gary Oak leaves Pallet Town on the same day as Ash in the Pokémon TV series.
Gary is Professor Oak’s grandson and Ash’s first major recurring rival. In the opening episode, both boys begin their journeys as Pokémon Trainers, although Gary receives his first Pokémon before Ash arrives at the laboratory.
Their rivalry continues through the Kanto and Johto storylines. Gary often travels with a larger entourage and presents himself as more accomplished than Ash, while Ash gradually proves himself through battles and League competitions. Their rivalry reaches a major early climax when they battle in the Silver Conference.
Gary is sometimes confused with later rivals such as Paul or Trip. Those characters belong to later regional stories, whereas Gary is specifically Ash’s childhood rival from Pallet Town and the earliest recurring competitor in the anime.