A new box storing information sorted for each individual or each prescribed department is to be registered with a first image processing apparatus, notification of a request to return a box name is transmitted to obtain additional information including a name(s) of a box(es) possessed by a second image processing apparatus. The second image processing apparatus responds to the notification by returning to the first image processing apparatus additional information including the name(s) of the box(es) that the second image processing apparatus possesses. The first image processing apparatus refers to the additional information obtained from the second image processing apparatus including the box name(s) to add to the new box the additional information including a box name and register the same.