An example game system includes a plurality of types of sub devices, and a main device capable of being attached to and detached from any of the sub devices, and executes a game application. The game system determines the type of the sub device to which the main device is attached while the game application is being executed. The game system executes a game process based on a game operation performed by using the main device and/or the sub device to which the main device is attached while the game application is being executed. The game system executes a game process depending on the determined type of the sub device.