Three years ago, shortly after Champion Brendan’s crowning and subsequent retirement, Hoenn was struck by a number of enormous meteors, which caused widespread devastation across the region. This catastrophe, also known as the Hoenn Catastrophe, significantly altered the landscape of Hoenn. Among other things, it rendered a large portion of the southern end of the region a barren wasteland and caused the Battle Frontier to be eradicated. This also had a significant impact on the animal population, leading to the extinction of a great number of species. Even more peculiarly, new Pokémon species, which came to be known as Meteoric Pokémon, started popping up all over the place. At the head of the pack stood three extremely potent and nefarious Pokémon…
The events of the story start when you arrive in Littleroot Town and are greeted by Professor Birch, who requests that you finish the Pokédex so that he can catalogue all of the new Pokémon. You talk to April, who is either Birch’s niece (or nephew), or Gordon, and you also talk to Billy, who is Wally’s younger brother. Wally is the current League Champion. In addition to that, Romero, the leader of the Petalburg Gym, has a younger brother named himself who is always appearing in your way. He goes by the name of Mosmero, and he is a very peculiar individual. In spite of the fact that he is an adult, he goes around the region playing various jokes on people.