Yumi Aoyama is now a girl diver in shallow waters to cut oysters and other shellfish delicacies, and eventually pearls, from the shallow underwater rocks, like so many poor girls of her village. She comes from a rich family, but the Aoyama's treasure has been buried in a great earthquake when she was a little girl, and with the treasure, her lost sister. Yumi tells Kyouko, a policewoman friend, that she has seen the ghost of her dead sister, telling her how to find the entrance to a cave where their family's treasure is. As Kyouko begins an investigation, she finds out that the ghost story is part of a conspiracy by a criminal gang, who is out looking for an easy way to access the enormous treasure. Girl divers' friendship and blood relations come to a halt when ghosts vanish and truth is exposed - culminating in some hand to hand fighting by the seashore. (Semi-documentary footage of actual Ama women diving and exploring underwater tunnels and caves.)
