1. A scanning system comprising: a pen-shaped scanner that scans a character string that is one part of a sentence described in a paper book and generates and transmits sentence image data on the basis of the scanned character string; a storage unit that book image data that is higher in image quality than the sentence image data and is obtained by electronically imaging the sentence described in the paper book is stored, and a matching unit that compares the book image data with the sentence image data that the pen-shaped scanner has transmitted and extracts partial image data that has been decided to match the sentence image data from the book image data.