Roman Porno from 1972.

The former Japanese Naval Academy was at Etajima, one of the many islands of the beautiful Inland Sea. Among the new cadets were Ishikawa and Murase. Murase's mother had remarried after his father's death and the impressionable boy hated his overbearing father who held the whip-hand over his gentle mother. Out of defiance of his step-father he became wayward. But he was bright and his teacher persuaded him to enter the Academy as he knew that if he left home, his mother need not feel apologetic towards her husband on his account. Discipline was strict, their studies were hard and, in between, all the new cadets received an ample share of beatings, at the hands of the senior cadets, for the slightest mistakes. Murase thought all picked on him the most, especially Cadet First Class Kogure, who manhandled him at the slightest excuse.