1. A data input system, comprising: an image reading device including: a reading unit that reads, on a form basis, an original image of each form filled with characters; a setting unit that extracts original image data pieces as a result of dividing, on a character basis, data of the original image of the form read by the reading unit, and sets identification information to each of the original image data pieces for defining positions thereof on the form; a generation unit that generates, for each of the original image data pieces extracted by the setting unit, character-associated information associated therewith; and an output control unit that makes an output with a correlation among the original image data pieces, the identification information set to each of the original image data pieces, and the character-associated information generated for each of the original image data pieces; and a data input receiving device including: a display control unit that displays any of the original image data pieces selected in accordance with a predetermined procedure from the original image data pieces provided by the output control unit; a receiving unit that receives an input of text data for use to identify which character is represented by each of the original image data pieces displayed by the display control unit; and a storage control unit that makes storage by correlating the text data received by the receiving unit with the original image data pieces displayed by the display control unit and the identification information set to each of the original image data pieces.