Ash explores the Kanto region in the first season of the Pokémon anime.
Pokémon: Indigo League follows Ash Ketchum as he leaves Pallet Town, receives Pikachu from Professor Oak, and travels across Kanto while challenging Gym Leaders and pursuing the Pokémon League.
Kanto is also the setting associated with the first-generation video games, Pokémon Red, Green, and Blue. Locations such as Viridian City, Cerulean City, and Pewter City connect the anime’s journey to the original game world.
Johto, Hoenn, and Sinnoh are later regions introduced in subsequent game generations and anime arcs. The Orange Islands appear after the Kanto League storyline, but they are a separate setting rather than the name of Ash’s first main region.