The story of “an uncelebrated magician”, written by a former teacher and education supervisor Teruo Ebashi, is a standard material of morality lesson in Japanese primary schools, in which the magician, a moral hero, fulfilled his promise to meet and amuse a lonely boy, at the cost of the once-in-a-lifetime opportunity of making his debut at a metropolitan theater. And its unwritten backstory was once told by the author in an interview: the magician had been deeply influenced by his tender-hearted parents who were always ready to help vulnerable people. In this paper, I discuss the merits of disclosing such a backstory to the students of a moral lesson, showing a suitable way of proceeding with the class. The points are as follows; (1) Merit 1: It helps the students identify the true components of a moral conduct (such as the doerʼs courage or the surrounding social milieu), and think concretely on what conditions they could do the same, thus feeling a proper sort and degree of reality in the story (or sympathy for the hero), while, on the other hand, discussing objectively how they can realize a societal milieu which makes it easier for individuals to behave morally. (2) Merit 2: It gives the students ①the recognition (which may enhance the cultural level of the people) that a conclusion is relative to term definitions, assumptions, preconditions, etc., and ②an experience of fallibilism, in which their conclusive opinions often change as they incrementally come to know the circumstances. (3) In order to avoid an irrelevant or far-fetched discussion, a story as a material of a moral lesson should be used not to learn a single virtue but to discuss a virtue and its “peripheral” such as other virtues (or moral values) or related political, economic, legal, literary, psychological, ethological issues, etc.