An information processing system including an image search system configured to: search, for an image to be found, a database in accordance with a search request and based on similarity thereof to a search key image, the similarity being determined by extracting feature information from the search key image and searching the database for feature information having a high similarity to the extracted feature information, the database having the image to be found and linkage information registered in association with each other; and transmit the linkage information associated with the image to be found to a transmitter of the search request when the image to be found is found, the information processing system comprising: an acquisition unit configured to acquire a captured image and the search request for requesting the searching in which the captured image is used as the search key image, the captured image having been obtained by causing a terminal device to capture an image of a medium; a search unit configured to perform the searching based on the search key image in accordance with the search request acquired by the acquisition unit and transmit, to the terminal device, the linkage information associated with the image to be found that is found as a result of the searching; and a notification management unit configured to transfer permission information to a notification unit when the image to be found that is found as a result of the searching based on the search key image is a particular image, the permission information enabling identification of the terminal device and indicating that providing a notification through push notification to the terminal device is permitted for a push-supporting application, the notification unit being configured to provide the notification via the push-supporting application to the terminal device, wherein the push-supporting application is configured to transmit, when a push notification for the push-supporting application installed on the terminal device is permitted, identification information for identifying the push-supporting application itself to and to request a notification ID from the notification managing unit, when the terminal device or the push-supporting application is started up. search, for an image to be found, a database in accordance with a search request and based on similarity thereof to a search key image, the similarity being determined by extracting feature information from the search key image and searching the database for feature information having a high similarity to the extracted feature information, the database having the image to be found and linkage information registered in association with each other; and transmit the linkage information associated with the image to be found to a transmitter of the search request when the image to be found is found, an acquisition unit configured to acquire a captured image and the search request for requesting the searching in which the captured image is used as the search key image, the captured image having been obtained by causing a terminal device to capture an image of a medium; a search unit configured to perform the searching based on the search key image in accordance with the search request acquired by the acquisition unit and transmit, to the terminal device, the linkage information associated with the image to be found that is found as a result of the searching; and a notification management unit configured to transfer permission information to a notification unit when the image to be found that is found as a result of the searching based on the search key image is a particular image, the permission information enabling identification of the terminal device and indicating that providing a notification through push notification to the terminal device is permitted for a push-supporting application, the notification unit being configured to provide the notification via the push-supporting application to the terminal device, wherein the push-supporting application is configured to transmit, when a push notification for the push-supporting application installed on the terminal device is permitted, identification information for identifying the push-supporting application itself to and to request a notification ID from the notification managing unit, when the terminal device or the push-supporting application is started up.