Aika, a bright and athletic high school student, proves her skills by passing the salvagers license test. Despite her competence, her youth and hot-headedness lead others to underestimate her, leaving her struggling to find work. Determined to utilize her license, she advertises her services at school. Erika, the affluent head of the treasure hunting club, takes notice and hires Aika for a sea salvage mission. Excited, Aika joins Erika, only to realize the daunting task ahead when she sees the advanced submarine and their destination. This revelation sparks a confrontation with a group of girls from the southern islands, including the enigmatic Karen. Thus commences Aika's thrilling new adventure!