The Sailor Who Fell From Grace With The Sea By Yukio Mishima

A band of savage thirteen-year-old boys reject the adult world as illusory, hypocritical, and sentimental. When the mother of one of them begins an affair with a ship's officer, he and his friends idealise the man at first; but it is not long before they conclude that he is in fact soft and romantic. They regard this disillusionment as an act of betrayal on his part - their retribution is deliberate and horrifying.