My interest in this stirring movie arose from a 2014 visit to Nagasaki where I attended a talk by a survivor of the Aug 9, 1945 atomic bomb blast.  The elderly Japanese gentleman mentioned that local Catholics could not understand why or how Christian Americans decided to drop the “Fat Man” bomb on them.  The blast’s epicenter was the district of Urakami, where St. Mary’s cathedral and Catholic community had been located.  
On hprweb.com, I subsequently read an interesting article by Br. Anthony Josemaria, entitled “The Catholic Holocaust of Nagasaki--- Why Lord?”   His article helpfully discusses recurring waves of persecution and suppression of the Christian religion after it had been brought to the Kuyshu region in 1549 by Portuguese missionaries led by Fr. Francis Xavier.