While playing on a beach, Pikachu and his Pokémon friends spot a mansion nearby. As they explore the grounds in search of their next fun activity, the group encounters an uptight Yogiras who maintains order around the residence and its garden.

Despite Yogiras' complaints, his own companions and Pikachu's party start a spirited game of hide-and-seek. When Yogiras kicks a rock in frustration at being ignored, it accidentally hits a lawnmower, activating its engine and causing it to chase after the Pokémon. With the runaway lawnmower putting everyone in danger, Pikachu, Yogiras, and all their friends must join forces to keep each other safe.