1. An information processing system, comprising: an input device that receives input of images captured by a plurality of imaging apparatuses including a first imaging apparatus and a second imaging apparatus: and an output device that outputs information on two individuals when each of the two individuals satisfies conditions of a moment of disappearing from the frame of an image of one of the first imaging apparatus and the second imaging apparatus and a moment of appearing in the frame of an image of the other one of the imaging apparatuses.