A system includes a biometric sensor that detects biometric data of a person in a first region and a presuming unit calculating, from the biometric data, a stress index and presuming that the person is a person to be tracked based on the calculated stress index. The system also includes a first camera acquiring first image data of the person in the first region and a second camera acquiring second image data of the person in a second region. The system further includes a monitoring unit that checks the second image data with the first image data corresponding to the target person to track the target person in the second region and determine whether the suspicious person enters the second region. The system also includes a warning unit that emits a warning when the monitoring unit determines that the target person enters the second region.