CONTROLLER, CONTROL METHOD, AND COMPUTER-READABLE RECORDING MEDIUM

A controller (10) includes an imaging unit (26), a reception unit (20), a detection unit (16C), and an opening/closing control unit (16D). The imaging unit (26) acquires an image of a peripheral area P of an opening/closing body (30) provided in a main body part (vehicle body (32)). The reception unit (20) receives, from a first terminal (12) that transmits a first signal of a predetermined strength, the first signal. The detection unit (16C) detects a motion of a subject (40) included in the image. The opening/closing control unit (16D) controls an opening operation of the opening/closing body (30) when a change in a reception strength of the first signal received by the reception unit (20) represents a change synchronizing with the detected motion of the subject (40).