Pokémon: Let's Go, Pikachu! and Let's Go, Eevee! are set in the Kanto region and include the original 151 Pokémon in addition to their respective Mega Evolved forms from Pokémon X, Y, Omega Ruby and Alpha Sapphire and their Alolan Forms from Pokémon Sun and Moon.
Let's Go, Pikachu! and Let's Go, Eevee! feature common elements of the main series, such as battling non-player character Pokémon Trainers and Gym Leaders with caught Pokémon creatures. However, when facing wild Pokémon, instead of battling them with the traditional battle system like in past games, the catching of Pokémon uses a system that is reminiscent of the mobile spin-off game Pokémon Go. By using the motion controls of the Joy-Con controller or Poké Ball Plus peripheral, players can throw berries to pacify a Pokémon or Poké Balls to attempt to capture it.[3][7] The action can also be performed with a button press when the Joy-Con controllers are docked to the console or in handheld mode, but this still requires using motion controls to aim.[8] If a player uses motion controls, the catching of Pokémon is based on the player's timing rather than accuracy. Although it is possible to miss a throw, the ball is almost guaranteed to make contact with the Pokémon.[9] One notable difference in Let's Go, Pikachu! and Let's Go, Eevee! is that wild Pokémon are visible from the overworld, rather than as random encounters in grass or in caves like in previous main series Pokémon role-playing games. To start an encounter with a wild Pokémon, the player must simply approach the Pokémon in the environment.[10]