An image forming system includes a portable terminal device, an image forming apparatus, and a marker registration circuit. A display device in the image forming apparatus displays a marker associated with location information of a user who has instructed execution of printing on a recording medium. The portable terminal device includes an information acquisition circuit and a position notification image output circuit. The information acquisition circuit photographs the marker displayed on the display device using an imaging device, so as to acquire the location information registered in the marker registration circuit, and the location information is associated with the marker photographed by the imaging device. The position notification image output circuit outputs a position notification image that notifies an output device of a position corresponding to the location information acquired by the information acquisition circuit.