Shiki, a young girl, leaves home in 2024 to reside with her grandfather, Taizou, who oversees the Ushio Sea Service on the man-made island-city of Standard Blue. Her father had passed away due to a deep sea accident four years ago, and she wishes to uncover her family's connection to the sea while learning about herself and her father. Taichunat and Takeshi, two members of the Ushio crew, initially view Shiki as a burden, but her bravery and passion quickly win them over. Shiki's mother appears, posing a threat, and Shiki must demonstrate her mettle.
