1. An image forming system comprising: an access unit for accessing a first image stored in a recording medium; a reductive color processing unit for forming a reduced background image by reducing a color gamut of the first image; a printer unit; an order sheet print control unit for causing the printer unit to print an order sheet on which the background image with the reduced color gamut is printed in a free rendering area; a composition unit for separating an area of a subject recorded by a user in the free rendering area from an image of the free rendering area read by a scan unit based on the reduced color gamut of the background image and superimposing the area of the subject on the first image to thereby form a composite image; and a composite print control unit for causing the printer unit to print the composite image.