Long ago, humans lived in the sea. However, some humans defied the Sea God and moved to the land, creating the division that now exists between Shioshishio, the Sea Village, and Oshiooshi, the village of the land. Now, four middle school students from the Sea Village, Manaka Mukaido, Hikari Sakishima, Chisaki Hiradaira, and Kaname Isaki must attend Mihama Middle School on the surface. While getting used to their new lives, these four and their new friend from the surface, Tsumugu Kihara, learn how true bonds of love and friendship can overcome any separation.