DRIVING ASSISTANCE DEVICE, DRIVING ASSISTANCE METHOD, NON-TRANSITORY COMPUTER-READABLE STORAGE MEDIUM, AND VEHICLE SYSTEM

A driving assistance device for a vehicle, the driving assistance device includes: a surrounding environment recognition unit that recognizes surrounding environment of the vehicle; a lane change prediction unit that predicts whether there is a possibility that the vehicle will change lanes; and a gaze recognition unit that recognizes a gaze of a driver; and a notification unit that performs notification by sound by controlling a speaker when it is predicted that there is a possibility that the vehicle will change lanes and there is a nearby vehicle on a lane into which the vehicle is going to change lanes, wherein the notification unit changes a notification mode based on a direction of the gaze.