Children of the sea

When Ruka was younger, she saw a ghost in the water at the aquarium where her dad works. Now she feels drawn toward the aquarium and the two mysterious boys she meets there, Umi and Sora. They were raised by dugongs at sea, and hear the same strange songs from the sea as she does. Ruka’s dad and the other adults are only distantly aware of what the children are experiencing as they get caught up in the worldwide mystery at the sea.