In Pokémon Pokopia’s story, humanity left Earth for outer space.
The game gradually reveals that unexplained environmental phenomena made the landscape inhospitable to life. Humans responded by departing the planet rather than remaining in the damaged region. Their absence is one of the central mysteries investigated by Ditto and Professor Tangrowth.
Humans could not take all their Pokémon with them, so they stored Pokémon in a massive computer system designed to continue operating after the departure. The system could release Pokémon when necessary, connecting the abandoned habitats to the wider history of the world.
This plot point is easy to confuse with a conventional disappearance story in which humanity vanishes without explanation. Pokopia instead gives the evacuation a technological and space-travel context. The game’s ending further reinforces that connection when a structure is revealed to be a rocket ship.