1. A non-transitory computer-readable storage medium storing a game program causing a computer comprising a display and a controller controlled by a user to function as: game space control means for generating a virtual game space; player object control means for generating a player object in the game space and causing the player object to act in the game space based on object operation information input from the controller; target object control means for generating a target object in the game space and causing the target object to act in the game space; game image generate means for generating a game image which is an image obtained by photographing the game space from a specific sight line by a virtual camera and displaying the game image on the display; target image display means for displaying a target image which is a small image for specifying the target object on the display; and lock on means for instructing the game image generate means to control the sight line of the virtual camera so that there exists at least a part of the target object specified by the target image in the game image when a lock-on operation is operated by the controller.