An image processing device, an image processing system, an imaging device, an image processing method, and a recording medium storing program code. The image processing device includes a receiver configured to receive a first image and a second image, a memory configured to store a joining position at each one of a plurality of portions between the first image and the second image received by the receiver, and circuitry configured to evaluate, for each of the plurality of portions, validity of the joining position in a past stored in the memory, and generate a composite image based on the first image and the second image received by the receiver and the joining position in the past stored in the memory on a site where the validity meets a criterion. The method includes reading a past joining position at each one of a plurality of portions between a pair of images.