1. An image processing device comprising: a determination unit configured to determine: whether a character included as a subject in a captured image by a camera is a non-main character on the basis of sight lines of the character, and whether a size of the non-main character is larger than a first predetermined threshold value; a posture recognition unit configured to identify a posture of a body of the non-main character; and a control unit configured to control, based on the determinations of the determination unit and the identified posture of the posture recognition unit, at least one image-related process selected from the group consisting of locking a shutter button, preventing the image from displaying, preventing the image from recording, and lowering sharpness of at least a part of the non-main character in the captured image.