To be fair, the film is based on a book, written by a Japanese Catholic, about the the real, brutal persecution of Christians in Japan during the early 1600s. The novel is highly regarded in Japan and there was a film version in the 70s by Masahiro Shinoda (Double Suicide, Assassination, Samurai Spy, Gonza the Spearman etc.) The people who suffered under the systematic killings of Christians were by large Japanese. The conflict of the book is not merely about trying to save the Japanese Christians from being persecuted, but also the meaning of martyrdom and the silence of God during horrific events.
I don't know how this is going to be a three hour movie though. The book is 200 pages, if that.