This was written as a sequel of 海と毒薬(The Sea and Poison).
As long as I know, there is no translation into English despite 海と毒薬 have.
Main Character of 海と毒薬 Suguro 勝呂 is also one of main characters.
In 海と毒薬 author compared Japanese moral with Western one and critisized weakness of Japanese conscience.
After long time from war, he might have a daubt "Is there absolute virtue ?".
In the Bible there is a word "Vengence Is Mine.".
But Mr. Endo's God never judge only weeps for his Sin.
He argued the Japanese have been able only to interplet the concept of Unique God like this.