1. An image processing device configured to provide a plurality of functions including a limited function, the limited function being usable to a permitted user in a limited operation mode, the image processing device comprising: a scanner configured to scan an image including an identifying image of a user who is registered in association with the image processing device and a processible image on a single sheet in a scanning direction, the identifying image being formed in an arbitrary area with the single sheet; a memory device comprising a first area and a second area; a control device configured to scan the image on the single sheet portion by portion from upstream to downstream sequentially along the scanning direction, wherein the scanning by the control device comprises: scanning an upstream portion of the single sheet, the upstream portion being an upstream part of the single sheet with regard to the scanning direction and being defined in a predetermined range in the scanning direction, obtaining image data from the scanned first portion of the single sheet; storing the obtained image data in both the first area and the second area in the memory device; and; determining whether the obtained image data stored in the first area includes the identifying image of the user associated with the limited function of the image processing device, the limited function being configured to process the obtained first image data and being allowed to be activated by the permitted user; wherein the scanning by the control device is activated while the image processing device is in the limited operation mode and when the limited function requested by the permitted user involves a scanning behavior using the scanner; wherein, when it is determined that the obtained image data stored in the first area does not include the identifying image of the user, the control device performs the scanning further with a downstream portion of the single sheet, the downstream portion being a downstream part of the single sheet with regard to the scanning direction and being defined in the predetermined range in the scanning direction, until the control device determines that the obtained image data stored in the first area includes the identifying image of the user associated with the limited function of the image processing device; wherein, when it is determined that the obtained image data stored in the first area includes the identifying image of the user associated with the limited function of the image processing device, the scanning by the control device further comprises: scanning a remaining portion of the single sheet downstream from the scanned portion; obtaining processible image data from the scanned remaining portion of the single sheet; storing the obtained processible image data in the second area and stop storing the obtained processible image data in the first area; and implementing the limited function of the image processing device based on the image data and the processible image data stored in the second area; wherein, when it is determined that the obtained image data stored in the first area does not include the identifying image of the user associated with the limited function of the image processing device, and if there is no further downstream portion to scan on the single sheet, the scanning is terminated and the control device informs the user of the termination of the scanning; and wherein, when it is determined that the obtained image data stored in the first area includes the identifying image of the user but the identifying image is not associated with the limited function of the image processing device, the scanning is terminated and the control device informs the user of the termination of the scanning.