DRIVING ASSISTANCE DEVICE, DRIVING ASSISTANCE METHOD, AND STORAGE MEDIUM

A driving assistance device includes a storage medium storing computer-readable instructions and a processor connected to the storage medium, the processor executing the computer-readable instructions to generate a target operation amount profile that is a time-series change in a target acceleration operation amount when a mobile object merges into a main lane, and cause an information output device to output information when an actual acceleration operation amount that is an amount of acceleration operation performed on an acceleration operator by a driver of the mobile object has deviated from a prescribed range including the target acceleration operation amount. Generating the target operation amount profile includes changing the target operation amount profile based on a driving tendency of the driver.