1. An image forming system comprising: a plurality of image forming apparatuses that form images; and a second memory that stores user identification information for identifying a user and apparatus identification information for identifying an image forming apparatus storing image data corresponding to the user identification information so as to be correlated with each other, wherein each of the image forming apparatuses includes a first memory that stores the user identification information and the image data so as to be correlated with each other; a reception component that receives user identification information of a certain user; a first acquisition component that acquires image data stored in the first memory provided in the image forming apparatus identified by the apparatus identification information correlated with the user identification information received by the reception component when the apparatus identification information correlated with the user identification information received by the reception component is stored in the second memory; a second acquisition component that acquires, from other image forming apparatuses which are different from the own image forming apparatus, image data correlated with the user identification information received by the reception component and apparatus identification information for identifying the image forming apparatus storing the acquired image data, when the apparatus identification information correlated with the user identification information received by the reception component is not stored in the second memory, or the image data correlated with the user identification information received by the reception component cannot be acquired by the first acquisition component; a storage controller that stores the apparatus identification information acquired by the second acquisition component and the user identification information received by the reception component in the second memory so as to be correlated with each other; and an image forming component that forms an image corresponding to the image data acquired by the first acquisition component or the second acquisition component.