Marine Snow no Densetsu

On Earth, a large-scale ocean city is being built to solve the ever-increasing population problem. The construction of the ocean city involves pouring massive amounts of concrete into the sea, polluting it in the process.

One day, a sudden explosion occurs at the ocean city construction site where Hiroshi Umino is working. The designer, Nami Shimaoka, becomes the prime suspect of the accident. In reality, Nami is an agent of the sea people, acting to prevent the ocean city project.

Although Nami's hometown is Ibusuki, she disappears after saying, “I'm going back to my snowy hometown.” Hiroshi, who loves her, believes in her and heads to Ibusuki. Meanwhile, the queen of the sea people, Izanami, resolves to resist the land people's invasion of the sea and issues a declaration of war.