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 Ketchum wakes up late one morning after having broken his alarm clock in his sleep. He eventually makes it to Professor Oak's lab, but is told that the three starter List of Pokémon (Bulbasaur, Squirtle, and Charmander) have already been taken by Trainers who were on time. However, Oak reveals that he has one more Pokémon, an Electric-type named Pikachu. Despite its volatile and feisty personality, as well as its refusal to get inside a Poké Ball, Ash happily takes Pikachu for his journey.
The story follows a young genius university professor who is able to learn any language. He is asked to decipher a code used in wireless communication: the Luger Code, developed by werewolves, enemies to mankind. Startled to find that he cannot decipher the code and desperate to study it, the professor embarks on a journey to capture a living werewolf to aid him.
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!