1. An image processing apparatus comprising: an obtaining unit configured to obtain a sensed image of a physical space on which at least one index is laid out, the sensed image being sensed by a sensing unit; a detection unit configured to detect at least one index in the sensed image; a generation unit configured to generate a virtual object to be displayed within a display region within the sensed image based on at least one index which is detected by the detection unit in a non-display region which is inside the sensed image and is outside the display region; an extraction unit configured to extract, as a display image, the display region from the sensed image; a composition unit configured to generate a composite image by compositing the display image extracted by the extraction unit and the virtual object generated by the generation unit, wherein the composite image does not include an index detected in the non-display region; and an output unit configured to output the composite image.