The Demon Comes in Spring 1989 on netflix

Island villagers find a young woman and young man swept ashore near their remote village in northeastern Japan. The two have tried to escape the girl’s enforced marriage to another man, in order that they may marry themselves. The ancient custom of the village decrees that the angry sea gods must be calmed by throwing the pair back into the sea. The lovers face being sacrificed to the sea gods or perhaps something even more difficult to bear.