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 and hear the same strange calls from the sea as she does.
After following Umi deep into the ocean, Ruka finds herself in an undersea cave where she hears a voice calling to her. She soon realizes it is the meteorite in her stomach, telling her the next step in her journey.
Story and art by Daisuke Igarashi.