1. An information processing device for inspecting a target image that contains an image of an inspection target, the information processing device comprising: a pre-processor configured to perform pre-processing for comparing the target image with a reference image or a plurality of reference images; a first calculator configured to define, in the target image, a region of interest (ROI) and surrounding regions that are adjacent to the ROI, and calculate a feature value of the ROI; a second calculator configured to calculate an outlier from comparison with feature values of images corresponding to the ROI and the surrounding regions in the reference images, the outlier numerically indicating singularity of an image at the ROI; and a determiner configured to provide, based on the outlier, an indicator to be used for the inspection.