In a world where people collect pocket-size monsters (Pokémon) to do battle, a boy comes across an intelligent monster who seeks to be a detective.
In the Forest of Okoya, Koko is a feral child who has been raised as a Pokémon by the Mythical Pokémon Zarude. Koko has grown up never doubting that he is a Pokémon even though he can't really use any sort of moves. Ash Ketchum and Pikachu meet Koko and help him protect the Great Tree from the crooked scientist Dr. Zed.
Ash meets the Mythical Pokémon Volcanion when it crashes down from the sky, creating a cloud of dust—and a mysterious force binds the two of them together! Volcanion despises humans and tries to get away, but it’s forced to drag Ash along as it continues its rescue mission. They arrive in a city of cogs and gears, where a corrupt official has stolen the ultimate invention: the Artificial Pokémon Magearna, created 500 years ago. He plans to use its mysterious power to take control of this mechanical kingdom! Can Ash and Volcanion work together to rescue Magearna? One of the greatest battles in Pokémon history is about to unfold!
Ash and friends (this time accompanied by newcomer Dawn) arrive at an idyllic village on their way to their next Pokemon contest, where chaos will soon erupt with the prophecy of two Pokemon Gods (Dialga and Palkia) and the arrival of a mysterious, seemingly deadly Pokemon named Darkrai, which has the power to distort space and time.
When Giratina is discovered to be able to create parallel dimensions, it's up to Ash and his friends to stop a mysterious stranger from using its powers for evil.
In the legendary past, before Poké Balls were invented, an aura-guiding hero Pokémon named Lucario sensed two groups of armies about to clash, and a threat of a massive war in front of Oldoran Castle in Kanto that would leave no survivors. He transferred this message to his master, the legendary hero Arlon, while he was being attacked by a violent group of Hellgar. During the battle, his sense of sight was lost and he was rendered unable to see. He used the detection of his Aura, and so with the offensive Wave Bomb, he eliminated them. Though by the threat, the queen of Rota, Lady Rin was resolute to die with her civilians, and so Arlon made a choice.
Deoxys, a Pokémon from outer space, terrorizes the high-tech city Ash Ketchum and his friends are visiting.
The devious leader of Team Rocket Organization, Giovanni, has a fervent ambition to take control of the Pokémon world through both financial and military means. To achieve his military needs, he covets a Pokémon stronger and more adept than any other, a veritable living war weapon, so he enlists a scientist named Doctor Fuji to create this being from the DNA of the ancestor of all Pokémon and most powerful of Pokémon, Mew, which Fuji had found on a previous jungle expedition. Fuji accepts, for he is heavily into the prospect of cloning to create and restore life itself, because of his love for his deceased daughter, Amber.
Little monsters run amok at a heavy metal festival.