1. An image processing apparatus comprising: a memory configured to store a program; and a processor configured to execute the program and perform a process including receiving an input specifying a target in a first captured image group that is obtained by slicing a three-dimensional body into a plurality of captured images at a first point in time, extracting a plurality of feature points surrounding the specified target from the plurality of captured images of the first captured image group, specifying slice positions of each of the plurality of feature points that are extracted in a plurality of captured images of a second captured image group that is obtained by slicing the three-dimensional body into the plurality of captured images at a second point in time, and outputting an image corresponding to a slice position range specified based on the specified slice positions of each of the plurality of extracted feature points, and corresponding to a range on a first plane specified based on positions of each of the plurality of extracted feature points on a second plane.