Yukio, a farm boy, and Toru, a fisherboy, live in a small Japanese village that is periodically threatened by a volcano on one side and tidal waves on the other. Yukio’s younger sister Setsu follows then and dreams of becoming a pearl diver. Toru is preparing to go fishing with his father when a bell tolls and a danger flag is hung high on the hill behind the village to warn of an impending tidal wave by the village patriarch, known as Old Gentleman. The fishermen consult the other village elders and decide that Old Gentleman is wrong and they will go on with their work. Old Gentleman comes down from his home and begs them to send their children to his hilltop home for their safety, but the refuse. That night, after Toru has gone to the home of his friend Yukio, a tidal wave destroys the village, leaving only a few survivors. Old Gentleman offers to take the orphaned Toru as his son but Toru, despite knowing he will live in wealth, decides to stay on with Yukio’s poor family. Ten years later, Yukio and Toru are as brothers. Toru is saving his money to buy a boat and Haruko, a diver, offers to sell him one of hers as she has fallen in love with him. Setsu has also fallen in love with Toru, while Yukio loves Haruko. On the day of the annual shark hunt, Yukio convinces Toru to join in helping kill the sharks, and they are joined by Haruko and Setsu. The girls get into a fight over Toru. Toru sees the fight and pulls Haruko off the smaller Setsu. Yukio sees him throw her aside and attacks Toru, declaring his own love for Haruko, while Toru reveals that it is Setsu whom he loves. Later, as Toru and Setsu discuss their wedding, Old Gentleman overhears their plans to go back to fishing. He hates the sea, as it killed his son thirty years ago, and offers them the biggest farm in the village if they will work it. He says he will not warn them of any more waves if the refuse. They do refuse, but tell him he will still warn them as he is a good man, but they will pay heed to his wisdom in the future.