1. An object monitoring system comprising: a memory storing instructions; and at least one processor configured to process the instructions to: create a state image by capturing a state occurring in a first range, create a monitoring target image by capturing a monitoring target present in a second range, detect a specific state from the state image, analyze a status of a monitoring target, using the state image from which the specific state is detected, and extract, from the monitoring target image, a feature used for specifying the monitoring target, based on the status of the monitoring target.