To provide an emulator capable of targeting a device capable of accepting connection of an expansion device for expanding a controller connection port to a plurality of controller connection ports. The emulator, targeting a device having at least one controller connection port and capable of accepting connection of an expansion device for expanding the controller connection port to a plurality of controller connection ports so as to accept connection of a plurality of controllers, emulates operation of the targeted device. The emulator assigns port identification information to each of controllers connected via wire or radio, the port identification information indicating to which of a controller connection port of the targeted device and the controller connection ports of the expansion device connected to the device the controller is assumed to be connected. The assigned port identification information is provided to a process for receiving an operation carried out on the controller.