An image forming system, comprising: an image forming apparatus (1A; 1B) configured to connect to a network; a directory server device configured to connect to the network and to include first registration information data (91a; 91b) on at least one of a domain group and a domain user; a user-manager server device configured to connect to the network and to include second registration information data (52; 53) on at least one of a local group and a local user that is separate from the first registration information data on the directory server device; and an authorization information registration device configured to (i) connect to the network, (ii) acquire first list data based on the first registration information data from the directory server device, (iii) acquire second list data based on the second registration information data from the user-manager server device, (iv) determine first authorization information on at least one of the domain group and the domain user within the first list data, (v) determine second authorization information on at least one of the local group and the local user within the second list data, (vi) register the first authorization information to the user-manager server device in association with at least one of the domain group and the domain user as first authorization information data, and (vii) register the second authorization information to the user-manager server device in association with the at least one of the local group and the local user as second authorization information data; wherein, the user-manager server device is further configured to transmit, (i) when a logged-in user belongs to the local group, the second authorization information to the image forming apparatus, and (ii) when the logged-in user does not belong to the local group, the first authorization information to the image forming apparatus. an image forming apparatus (1A; 1B) configured to connect to a network; a directory server device configured to connect to the network and to include first registration information data (91a; 91b) on at least one of a domain group and a domain user; a user-manager server device configured to connect to the network and to include second registration information data (52; 53) on at least one of a local group and a local user that is separate from the first registration information data on the directory server device; and an authorization information registration device configured to (i) connect to the network, (ii) acquire first list data based on the first registration information data from the directory server device, (iii) acquire second list data based on the second registration information data from the user-manager server device, (iv) determine first authorization information on at least one of the domain group and the domain user within the first list data, (v) determine second authorization information on at least one of the local group and the local user within the second list data, (vi) register the first authorization information to the user-manager server device in association with at least one of the domain group and the domain user as first authorization information data, and (vii) register the second authorization information to the user-manager server device in association with the at least one of the local group and the local user as second authorization information data; wherein, the user-manager server device is further configured to transmit, (i) when a logged-in user belongs to the local group, the second authorization information to the image forming apparatus, and (ii) when the logged-in user does not belong to the local group, the first authorization information to the image forming apparatus.