The setting of Pokémon Sun and Pokémon Moon is the Alola region. It consists of four tropical islands as well as an artificially created island. Many never-before-seen Pokémon inhabit the lush islands of Alola. The story begins shortly after the main character moves to Alola. Once players decide whether they want to play as a boy or a girl, they can choose their name and appearance. As soon as they arrive, their adventure begins, where they will encounter many fascinating people.

The Pokédex is a useful device that records information about the Pokémon the player sees and catches during their adventure. In Pokémon Sun and Pokémon Moon, the player receives a very special Pokédex from Professor Kukui, called the Rotom Pokédex. It houses a Rotom, a Pokémon that can inhabit electronic devices. The Rotom Pokédex can do much more than just register Pokémon - it has its own personality. It shows the player on the map where they are currently located and where they need to go next. Additionally, it provides hints about the next objective based on conversations with other characters.

In Pokémon Sun and Pokémon Moon, there is a feature called QR Code Scanner, which allows players to obtain information about a Pokémon by scanning the QR code for that Pokémon. This enables them to register the Pokémon of the Alola region in their Pokédex and find out where their habitats are. If players scan the QR code of a Pokémon they have not yet caught, they can locate it in this way.