System and service providing apparatus

A method performed in a system including a first service providing system that includes a hardware processor to provide a service to an apparatus and a second service providing system that includes another hardware processor to provide an external service and has an authentication infrastructure different from that of the first service providing system, the apparatus, the first service providing system, and the second service providing system being connected through a network, the method comprising:

• receiving, by the first service providing system, a permission request, from the apparatus operated by a first user, of requesting that a second user uses the second service providing system;
• changing, by the first service providing system, a connection destination of the apparatus to the second service providing system;
• causing, by the first service providing system, the second service providing system to perform a permission process;
• receiving, by the first service providing system, permission information indicating that the permission request is admitted for the second user from the apparatus;
• acquiring, by the first service providing system, a permission token for using the second service providing system by using the permission information from the second service providing system;
• and
• providing, by the first service providing system, the permission token associated with the second user based on a request for a process using the second service providing system, the request being received from another apparatus which is connected to the second service providing system and operated by the second user,
• receiving, by the second service providing system, the permission token, validating the permission token, and permitting the another apparatus to use the second service providing system.