In Pokémon Pokopia, the player-controlled Ditto imitates a human.
This transformation is the game's defining premise. Ditto uses its natural transformation ability to take on a human-like appearance, allowing the player to experience the world through a character that can interact with the environment in a human-shaped form.
The human imitation does not turn Ditto into a separate species or replace Ditto as the protagonist. It remains Ditto, but its chosen appearance explains why the player can perform activities such as gathering materials, crafting objects, building structures, and reshaping land.
The idea also creates a playful contrast with ordinary Pokémon stories, in which humans usually raise, battle, or study Pokémon. In Pokopia, the transformed Ditto takes an active role in rebuilding a home for Pokémon. The answer is therefore “a human,” rather than a particular named human character.