Methods and apparatus provide for: performing information processing on the basis of data received from a device that detects a target object; generating an image to be displayed as a result of the information processing; determining that a user needs to be warned when the target object moves out of a play area set in an object space in reference to a detection field of the device, the determining including causing the generating to superpose a warning image on the image to be displayed; and transmitting data of the image generated by the image generating section to a display device, where the determining includes setting positions of boundary surfaces of the play area with respect to boundary surfaces of the field of the device within a predetermined range from the user.