1. An explanatory-description adding apparatus comprising: a storage unit that stores scene metadata as combinations of a scene at a certain time in video contents and a group of metadata representing characteristics of the scene; an input unit that input a scene group including a plurality of the scenes; a retrieving unit that retrieves a group of metadata corresponding to the respective scenes included in the scene group, from the scene metadata; and an adding unit that selects combinations of the metadata in which a distance among the metadata included in the group of metadata is maximum, as explanatory descriptions for distinguishing the respective scenes, and adds the combination of the metadata to the distinguished respective scenes.