A young boy named Ash Ketchum embarks on a journey to become a "Pokemon Master" with his first Pokemon, Pikachu. Joining him on his travels are Brock, a girl-obsessed Rock Pokemon Trainer, and Misty, a tomboyish Water Pokemon Trainer who may have a crush on him. Ash and Co. end up traveling through various regions, including Kanto, the Orange Islands, and Johto, and then enter the Pokemon League competitions there. Along the way, they run into many confrontations with Jessie, James, and Meowth, a trio of Pokemon thieves who are apart of an evil organization called "Team Rocket". But everytime Team Rocket try to do their evil deeds, they fail thanks to Ash and his Pokemon.
After participating in the Johto League, Ash decides to begin anew in yet another journey; this time by himself and Pikachu, in the land of Hoenn. Though he isn't alone for long, as 10 year old May(whom dislikes Pokemon, but just wants to come along to see the world) travels with him after Pikachu destroys her bicycle. Ash also meets up with his old companion, Brock, and May's younger brother, Max. Together, they travel along in Hoenn, battling Gym Leaders, entering Contests, and other events on the way to the Hoenn League.
The journey of young Satoshi (Ash Ketchum) of Kanto continues as he arrives in the Isshu (Unova) region, still aiming to be a Pokémon Master; he and his partner Pikachu meet up with new comrades Iris and Dent (Cilan). As Satoshi challenges the Gyms of the Isshu region and battles new rivals, there is danger lurking behind the scenes as criminal syndicates Team Rocket and Team Plasma each have their own dark agendas for all the people and Pokémon who reside in Isshu.
Hikari is a 10 year old girl that wants to be a top coordinator just like her mother. She recieves the starting Pokemon - Pochama, after saving it from an Ariados's attack. Meanwhile, after conquering the Battle Frontier and motivated by his old rival Shigeru, Satoshi sets off to the far away land of Shin'ou. Once there, he meets Hikari and is reunited by his old friend Takeshi. Hikari - aiming to be top coordinator, and Satoshi - aiming to be a Pokemon Master and battle in the Sinnoh League, venture in the land of Shin'ou...Meeting lots of new Pocket Monsters, "Pokemon" for short, along the way.