1. An information processing device comprising: circuitry including a processing device and a memory encoded with instructions that, when executed by the processing device, implement: a detection unit configured to detect at least one mesh including a horizontal direction position of a target sound image in a horizontal direction, of meshes that are a region surrounded by a plurality of loudspeakers, and specify at least one mesh boundary that is a movement target of the target sound image in the mesh; a calculation unit configured to calculate a movement position of the target sound image on the specified at least one mesh boundary that is the movement target, based on positions of two of the loudspeakers present on the specified at least one mesh boundary that is the movement target, and the horizontal direction position of the target sound image, wherein the target sound image is outside all of the meshes and wherein the horizontal direction position of the target sound image is fixed and the target sound image is moved only in a vertical direction from a vertical direction position of the target sound image to the calculated movement position on the specified at least one mesh boundary that is the movement target in response to calculating the movement position of the target sound image on the specified at least one mesh boundary; and a gain adjustment unit configured to adjust a sound signal and to output adjusted sound signals to respective ones of the plurality of loudspeakers based on the calculated movement position of the target sound image.