The main character is asked to test out the PokéHelper, a new device of Professor Oak's that is used to talk to Pokémon. The player then meets a wild Pikachu and befriends it. Once the player earns Pikachu's trust, it will come and live in the player's house. There are three different activity days: Pikachu's Daring Days, Discovery Days, and Play Days. Each day has a different objective (e.g. collecting food, going fishing) and the player can earn Pika Points, the currency used at Abra's Shop to unlock new items.
After 365 gameplay days, Professor Oak notifies the player that Pikachu, still a wild Pokémon, must be released. The player ventures to the woods to find Pikachu and repeatedly says "goodbye", upon which Pikachu realizes it must return to the wild. After the credits, while the player looks around the front yard and reminisces, Pikachu returns, and the game continues as if Pikachu was never released.