1. An information processing device having a processor, comprising: two touch sensors each including a detection surface for detecting a position of an object thereon, the two touch sensors being arranged to be opposed to each other; wherein the processor determines a reference point and a reference axis based on one or a plurality of positions detected by one touch sensor of the two touch sensors; and the processor evaluates a content detected by another touch sensor of the two touch sensors based the reference point and the reference axis to determine a content of an operation input of a user, wherein the processor determines the reference axis, a direction of the reference axis, and positive and negative directions along the reference axis using three or more positions detected by the one touch sensor, and wherein the processor determines a direction indicated by the user as a direction relative to the positive and negative directions along the reference axis from the content detected by the another touch sensor, wherein the processor determines a rectangle having a smallest area including all of the three or more detected positions, and determines the reference axis in a direction parallel to a long side of the rectangle.