PORTABLE DEVICE, DRIVING ASSISTANCE SYSTEM, CONTROL METHOD, AND STORAGE MEDIUM STORING A CONTROL PROGRAM

A portable device, including: an unlocking portion configured to enable an operation for unlocking a door of a vehicle; and a processor, wherein, when the unlocking portion is operated in a case in which a reception sensitivity of a predetermined signal that is transmitted by wireless communication from the vehicle is a first sensitivity, the processor is configured to change the reception sensitivity to a second sensitivity that is a higher reception sensitivity than the first sensitivity.