Pokémon Pokopia takes place in a post-apocalyptic version of the Kanto region.
The setting is a damaged world that humans have abandoned and that has become difficult for Pokémon to inhabit. Ditto begins the story in this environment and works to restore habitats so Pokémon populations can recover.
Kanto is one of the most recognizable regions in Pokémon history, having debuted in Pokémon Red and Green in Japan and Pokémon Red and Blue internationally. Pokopia reimagines it in a very different state from its familiar adventure-game appearances: the focus is not on visiting gyms or challenging an Elite Four, but on rebuilding a livable world.
The setting is sometimes described generally as an unnamed ruined Pokémon world, but the game specifically identifies it as a post-apocalyptic version of Kanto. The environmental mystery and abandoned human infrastructure provide the background for Ditto’s restoration work.