The small, round black circle you can see on the corner of the bumper is the Estima parking sonar. This was a factory option on many Toyota models and was available separately for front and rear. The system is activated with a button near the driver’s right knee and uses an intermittent high pitched tone to warn the driver when the vehicle approaches a set distance to objects.
As the vehicle moves closer to the object the sound increases in frequency until it becomes a continuous unbroken tone when only a few centimetres from the object. There is also a verbal warning in Japanese in some cases.