Since long ago,human civilization had lived on the ocean floor.however,there were many humans who wanted to live above the surface and they moved to land creating a fundamental separation between the two.After four 14-year old middle school students from the sea village,shioshishio,have to attend Mihama middle school on the surface.What follows is their struggles to adjust to a new environment and the relationships between the sea and land people,while dealing with their own newfound feelings that have just started appearing with the end of their childhood.