In her final memory, Natsu Iwashimizu shares cherished meals with her family. However, upon waking, she discovers she's on a sinking ship, saved by three unfamiliar faces: Arashi Aota, whose kindness is matched only by his short fuse; Semimaru Asai, who teases Natsu's shy demeanor; and Botan Saotome, a skilled individual who grasps the gravity of their situation. Together, they manage to escape and navigate towards a deserted island.
Unbeknownst to them, this enigmatic land is actually post-apocalyptic Japan. A meteorite impact has eradicated human life and transformed the planet's ecosystem. To repopulate the earth, the government initiated the "7 Seeds" program, sending five teams—Spring, Summer A, Summer B, Autumn, and Winter—each comprising seven resilient youth and a guide. Natsu and her crew belong to Summer B, deemed social outliers.
Their survival hinges on finding one of seven government shelters for supplies. In a perilous, alien world devoid of familiar support, the quartet must learn to work together to endure.