In a future where global warming has flooded much of the Earth, 15‑year‑old Maia Mizuki, an orphan who just graduated from middle school, has applied to join the elite paramilitary Ocean Agency, a branch of the futuristic world government. Admission is limited to the smartest, most physically capable students, and Maia is poised to become one of the few selected. However, her dream life shatters when she unexpectedly fails the entrance exams. Soon after, she is evicted from her home, pickpocketed, taken hostage, and shot. She is rescued by two women, Rena and Shizuka, who belong to an unconventional aid organization.