A control device generates a first image in which, together with an object in the real world appearing in an image captured by a camera of a robot, a virtual object appears and which presents an exterior appearance of the virtual object while the position of the camera of the robot is set as a view-point. An HMD displays the first image generated by the control device. In a case in which the position of the HMD in the height direction changes, the control device generates a second image from which the object in the real world is deleted and which presents the exterior appearance of the virtual object viewed from a new view-point according to the change in the position of the HMD in the height direction. The HMD displays the second image in place of the first image.