An information processing system comprising: a user management server; and a plurality of client devices, each used by one of a plurality of users; the user management server including a user information storage section adapted to store, for each of the plurality of users, an identification name uniquely identifying the user in association with a restricted disclosure name registered by the user and information identifying, of the plurality of users, a user entitled to disclosure to whom the disclosure of the restricted disclosure name is permitted; each of the client devices including an application execution section adapted to execute an application program, and a user information request section adapted to transmit, to the user management server, a request for acquisition of name information of a requested user including information identifying a requesting user who uses the client device in response to an instruction from the application execution section; the user management server further including a user information request reception section adapted to receive the request for acquisition of name information transmitted from the client device, and a user information transmission section adapted to transmit the restricted disclosure name of the requested user as a reply to the acquisition request if the requesting user is registered as a user entitled to disclosure of the requested user; the application execution section showing, on a display screen, the name information of the requested user in accordance with the nature of information transmitted from the user information transmission section. a user management server; and a plurality of client devices, each used by one of a plurality of users; the user management server including a user information storage section adapted to store, for each of the plurality of users, an identification name uniquely identifying the user in association with a restricted disclosure name registered by the user and information identifying, of the plurality of users, a user entitled to disclosure to whom the disclosure of the restricted disclosure name is permitted; each of the client devices including an application execution section adapted to execute an application program, and a user information request section adapted to transmit, to the user management server, a request for acquisition of name information of a requested user including information identifying a requesting user who uses the client device in response to an instruction from the application execution section; the user management server further including a user information request reception section adapted to receive the request for acquisition of name information transmitted from the client device, and a user information transmission section adapted to transmit the restricted disclosure name of the requested user as a reply to the acquisition request if the requesting user is registered as a user entitled to disclosure of the requested user; the application execution section showing, on a display screen, the name information of the requested user in accordance with the nature of information transmitted from the user information transmission section.