Transmission data including at least data regarding luminances of a plurality of small areas obtained by dividing the entirety of an at least partial area of a captured image captured by an image capturing unit is acquired. Then, using the acquired transmission data, and based on a luminance of the entirety of the at least partial area of the captured image and the luminance of any of the plurality of small areas, a shape of an image capturing target and/or a position of the image capturing target relative to a data transmission device are determined, and based on the result of the determination, predetermined information processing is performed.