1. An image processing device comprising: circuitry configured to detect a feature point from stored moving image data; associate the feature point with additional information, the feature point being selected based on feature point selection information, wherein the additional information includes image data that is displayed as added to a reproduction of the stored moving image data; analyze a changing behavior of the feature point through the reproduction of the stored moving image data; generate data indicating change content to change display of the image data of the additional information associated with the feature point based on motion information indicating the behavior of the feature point analyzed and a display scenario indicating a change pattern to change the additional information associated with the feature point according to the behavior of the feature point; and control a display device to display the reproduction of the stored moving image data and to display the image data of the additional information based on the change content such that the image data of the additional information has motion corresponding to motion of the feature point of the stored moving image data, wherein when selection information to select at least two feature points, including the detected feature point, is input, the circuitry is configured to generate data to generate a display size of the additional information according to a distance between the at least two feature points.