A mediation service accepts a coordination instruction for coordinating a web application server with a coordination device from a web browser, generates a script to be authenticated by an authentication method corresponding to the server, and transmits the generated script to the coordination destination service providing system indicated by the coordination instruction. The web browser transmits authentication information or an authentication token, which is obtained in response to an input operation on an authentication information input screen displayed by execution of the script, to the coordination device. Then, the coordination device receives and saves the authentication information or the authentication token.