A method includes: associating content with erasure completion information indicating the content has been erased; forming an image of the content and an image at a time of formation indicating the erasure completion information; in a case where an erasure image is formed to be superimposed on at least a part of the image of the content on the recording medium, forming an image at a time of discarding indicating the erasure completion information and the erasure image, where the image at the time of discarding is associated with the content; and in a case where the erasure completion information is identified by the image at the time of formation and the image at the time of discarding included in single image data output when the image capturing device image-captures the recording medium, determining that the content associated with the erasure completion information has been erased.