The movie takes place in the present day, where Ash Ketchum and his friends, Pikachu, Serena, Clemont, and Bonnie, are visiting the ancient Alola region. While exploring the area, they stumble upon the mystical Hoopa, a Pokémon with the power to warp time and space. However, their excitement is short-lived, as they soon discover that Hoopa's powers have been hijacked by the nefarious Diancie, a Pokémon with the ability to create diamonds.