Pokémon Masters EX tells several stories, on the artificial island of Pasio. Here are their outlines, based on Poképédia.
The World Pokémon Masters
Defeated by a mysterious “Trainer in a cap,” Alexis, prince of a distant land, has the island of Pasio built and organizes the World Pokémon Masters, or WPM. Its rules: each Trainer uses only one Pokémon, on a team of at least three. The hero, or heroine, signs up with their Pikachu, forms a trio and travels across Pasio to defeat the five WPM Champions and win their badges. Along the way, they recruit other Sync Pairs and face Team Break, a band of masked thieves determined to ruin the tournament. This storyline has 30 chapters and 7 interludes.
The Evil Organization
A second storyline, in 9 chapters and one interlude, features the criminal organizations of the various regions, gathered on Pasio.
Arceus
A third storyline, with a prologue and 9 chapters, is devoted to Arceus.
Stories
Each Sync Pair has its own Stories, little tales to play through once it is recruited; some make its Pokémon evolve. Limited-time events regularly add Sync Pairs, such as Giovanni and Mewtwo, who arrived in December 2019, or Red and Charizard, able to Mega Evolve, in February 2020.
