The main character, a young tgirl named Nora, and her sister, a researcher, arrive in a foreign fishing village. There, rumors are circulating that “fish that live in the sea,” which were supposed to have become extinct long ago, have survived. While her sister embarks on a deep-sea expedition in her submarine, Nora also witnesses a mysterious shadow in the sea. Despite her misgivings, Nora begins her life in the village, but she has a hard time adjusting to the local children. Can her sister confirm the truth of the rumors, and what is the identity of the shadow Nora saw?