1. An image processing apparatus, comprising: a storage unit that is capable of storing a look-up table having one or more pieces of association information for associating a whole or part of one or more first images with a whole or part of at least one second image, which is an image whose load on a brain has been adjusted compared with that of the first image and which is an image of a same object as the first image; an image accepting unit that accepts one or more images; a mapping unit that acquires a whole or part of one or more second images associated with a whole or part of the at least one image accepted by the image accepting unit, using association information from among the one or more pieces of association information; and an image output unit that outputs at least one output image, which is the whole of the at least one second image acquired by the mapping unit or a group of part of the at least one second image acquired by the mapping unit.