1. An image processing device comprising: storage; and a processor configured to at least: acquire a time series of images from each of a plurality of imaging devices; track position of a target object in each time series of images; control storing, in the storage, distributions of feature values for respective regions into which each image of a respective time series of images is divided based on an imaging range of an imaging device corresponding to the respective time series of images; extract observed values corresponding to feature values in the regions of images in respective time series of images; acquire feature amounts based on deviation values of the observed values in the distributions of feature values; and associate tracked target objects with one another among multiple time series of images acquired from the plurality of imaging devices based on the feature amounts.