An image processing apparatus includes a memory and processing circuitry. The memory sequentially stores a plurality of read images read by a reading device. The processing circuitry transfers pairs of read images from the memory to an external apparatus in ascending order of priority in bookbinding to leave pairs of read images in the memory in descending order of priority in bookbinding. The processing circuitry further instructs an image forming device to execute image formation with pairs of read images in descending order of priority in bookbinding.