1. An image forming system comprising: an access unit for accessing a user image stored in a recording medium; a reductive color processing unit for forming a background image by reducing a color gamut of the user image; an order sheet print control unit for causing a printer unit to create an order sheet on which the background image 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 a color gamut of the background image and superimposing the area of the subject on the user image to thereby form a composite image; and a composite print control unit for causing the printer unit to print the composite image.