An HMD is coupled to a smart phone. The HMD displays a first image overlapping an external scene in a left display unit, and displays a second image corresponding to the first image overlapping the external scene in a right display unit. The smart phone includes a display panel displaying a third image, a first detector detecting that at least one of the first image and the second image overlaps the third image, and an adjustment unit adjusting, based on a detection result of the first detector, at least one of the first image and the second image such that the third image is visible.