1. An image processing system comprising: an illumination unit configured to emit near infrared light in an imaging area; a first capture unit configured to capture only a near infrared image of at least a part of the imaging area; a second capture unit configured to capture a natural image of at least the part of the imaging area; an area of interest setting unit configured to set an area of interest in one of the near infrared image and the natural image; and an image processing unit configured to extract an image inside the area of interest from the near infrared image, use the image extracted from the area of interest as a mask, and extract the mask from the natural image.