Breaking the conventions of prior Pokémon games, you play as a human who has suddenly been transformed into a Pokémon, but before you could come to grips with this startling revelation, a Butterfree needs help! Its baby Caterpie has fallen into a dungeon and cannot get out!

You and other Pokémon you befriend along the way must brave randomly created dungeons to help out other Pokémon who find themselves in need of rescuing or just need something delivered.

Unlike previous Pokémon games, the battles take place on the map (though they are still turn based), and although you may only directly control the Pokémon that represents you in the game, you can give your companions vague battle orders, such as use more special attacks or conserve items.