When retrieving information relating to another user of a different SNS, the CVR of an SNS can be effectively increased by displaying a social graph. According to the invention, by means of a social graph display program (API), user identifying information corresponding to user-to-user relationship information meeting predetermined conditions can be extracted by searching a database of information related to the other users of application programs A-C, in accordance with identifying information of a user A who has made a friend request. Thus the application program A displays, as candidates for the friend request, users corresponding to user identifying information returned from the social graph display program (API).