1. An image processing device, comprising: circuitry configured to store feature data indicating a feature of appearance of an object, generate an environment map representing a position of one or more objects existing in a real space based on an input image obtained by imaging the real space using an imaging device and on the stored feature data, and generate an output image by erasing an erasing target object from the input image based on a position of the erasing target object being one of the one or more objects existing in the real space recorded in the input image and represented in the environment map, and based on a position of the imaging device, wherein the erasing target object is an object recorded by the imaging device in the imaging of the real space at a time of the imaging of the real space, and wherein the circuitry is further configured to estimate a position of a floor surface or a wall surface in the real space based on a position of a point on a surface of an object other than the erasing target object represented by the environment map, and generate a CG image based on the position of the floor surface or the wall surface in the estimated real space.