Aika Sumeragi, a high school age C-Class salvager, is hired by class president Eri Shinkai to pilot her salvaging vessel. After introducing Aika to the treasure hunting club, and revealing coordinates hidden in a marking on fellow classmate Karen Minamino's chest, they embark on an adventure to see where it leads.

After arriving at the coordinates, Eri decides the treasure hunting club needs a break and declares that they will have a beach party on a nearby island. They are not alone, however, and Aika has to fight her teacher to protect Karen.