Aika, a high school girl, possesses intellect and athletic abilities. Her success in obtaining a C-class license for salvaging highlights her competence. However, her young and impulsive personality leads to Gota treating her like a child. Consequently, she struggles to find a salvaging job due to her reputation. In a bid to find work, Aika advertises her services in school, which catches Erika's attention. Erika, the wealthy leader of the treasure hunting club, hires Aika for a salvage job. Excited, Aika agrees without knowledge of the destination or equipment until she boards Erika's cruiser with a state-of-the-art submarine. Once Aika discovers the true nature of the job, she clashes with a group of high school girls on a southern island. The arrival of the mysterious Karen adds to Aika's latest challenge.