1. A driving-support-image generation device installed within a host vehicle and operatively connected to a navigation device and a display installed within the host vehicle, the driving-support-image generation device comprising: a computer processor; and a memory storing instructions which, when executed by the computer processor, performs a process comprising: recognizing a character in an image captured by an image capturing device mounted to the host vehicle, the image being indicative of a message content of a messaging object posted on a road or around a road, determining whether or not the recognized character corresponds to information related to a destination point or a route point of the host vehicle set in the navigation device, generating a driving-support image in which the recognized character that has been determined to correspond to the information related to the destination point or the route point of the host vehicle is highlighted, and causing the driving-support image to be displayed on the display.