An image processing system comprises a generating unit that reads documents and generates a read image including document images; an extracting unit that extracts each of the document images; a character recognizing unit that performs character recognition processing on each the document images; a determining unit that determines whether first information and second information have a pair relationship, the first information being any one of recognition results obtained on one side of the document images, and the second information being any one of recognition results obtained on the other side of the document images; and a registering unit that registers pieces of information for the recognition results corresponding to the one side and to the other side respectively including the first information and the second information which are determined that both pieces of information have the pair relationship, as information for a piece of the documents, in a storage unit.