A communication terminal communicably connected with a server, including circuitry to: detect one or more objects in any one of one or more images that are sequentially captured with an imaging unit; count a number of object detections, every time a predetermined number of objects are detected in the image; and transmit, to the server, one or more items of image data each including each one of the detected one or more objects, based on a determination that the counted number of object detections reaches or exceeds a predetermined value.