1. An image processing device comprising: an image processing unit configured to generate an output image using a first image obtained by imaging a real space from a first viewpoint as an input image, wherein, based on a position and a posture of the first viewpoint in the real space, the image processing unit generates, as the output image, a second image obtained by virtually imaging the real space from a second viewpoint having a position and a posture different from the position and the posture of the first viewpoint in the real space.