An information processing system comprising: a first information processing device; a second information processing device; and a control unit configured to perform a control of synchronizing a first image display application executed by the first information processing device and a second image display application executed by the second information processing device, wherein: the control unit is configured to synchronize image information displayed on the first information processing device and image information displayed on the second information processing device, the first and the second information processing devices are configured to set a shared area inside a display area for image information, the control unit is configured to synchronize image information displayed in the shared area, the first and the second information processing devices are configured to set a temporary saving area inside the display area for image information, and in addition, move the image information between the shared area and the temporary saving area, based on an input operation by a user, and if one information processing device from among the first and the second information processing devices moves one piece of image information from the shared area to the temporary saving area, the control unit is configured to move the one piece of image information displayed in the shared area of the other information processing device to the temporary saving area, wherein the temporary saving area is configured to save temporarily said one piece of image information. a first information processing device; a second information processing device; and a control unit configured to perform a control of synchronizing a first image display application executed by the first information processing device and a second image display application executed by the second information processing device, wherein: the control unit is configured to synchronize image information displayed on the first information processing device and image information displayed on the second information processing device, the first and the second information processing devices are configured to set a shared area inside a display area for image information, the control unit is configured to synchronize image information displayed in the shared area, the first and the second information processing devices are configured to set a temporary saving area inside the display area for image information, and in addition, move the image information between the shared area and the temporary saving area, based on an input operation by a user, and if one information processing device from among the first and the second information processing devices moves one piece of image information from the shared area to the temporary saving area, the control unit is configured to move the one piece of image information displayed in the shared area of the other information processing device to the temporary saving area, wherein the temporary saving area is configured to save temporarily said one piece of image information. the control unit is configured to synchronize image information displayed on the first information processing device and image information displayed on the second information processing device, the first and the second information processing devices are configured to set a shared area inside a display area for image information, the control unit is configured to synchronize image information displayed in the shared area, the first and the second information processing devices are configured to set a temporary saving area inside the display area for image information, and in addition, move the image information between the shared area and the temporary saving area, based on an input operation by a user, and if one information processing device from among the first and the second information processing devices moves one piece of image information from the shared area to the temporary saving area, the control unit is configured to move the one piece of image information displayed in the shared area of the other information processing device to the temporary saving area, wherein the temporary saving area is configured to save temporarily said one piece of image information.