Which enhanced Game Boy game features Pikachu as its central partner?

Pokémon Yellow is the enhanced Game Boy game that features Pikachu as the central partner.

Released in Japan on September 12, 1998, Pokémon Yellow was based on Pokémon Red and Blue but added elements inspired by the anime. Pikachu follows the player outside its Poké Ball and reacts to the player’s actions.

The game changes the starter structure of the earlier versions. Instead of choosing Bulbasaur, Charmander, or Squirtle at the beginning, the player receives Pikachu. The three original starters can later be obtained during the adventure.

Pokémon Yellow is also known as Pokémon Yellow Version: Special Pikachu Edition. It is not the same as Pokémon Gold or Silver, which began the second generation, and it predates the later Nintendo 3DS virtual-console release.