In 2024, young Siki runs out of the house to live with her grandfather Taiy, who heads the sea service of the Ushio in the artificial island city of Standard Blue. Four years ago, Siki's father died as a result of an incident in the deep sea, and Siki is now trying to learn about their father, about himself and about the deep relationship of their family with the sea. The crew of the ears-Takeshi, Taichun-at first considers Siki obstacle, but she wins them with their enthusiasm and courage. However, when the chic mother comes after it, the danger is approaching, and the chic is subject to the final test.