The story is set on Okinawa's isolated island of Iwado, which has seen a growing movement advocating a return to an autonomous government. Ao Fukai, a 12-year-old boy with a missing father, lives on the island with an old doctor named Toshio and is about to enter middle school. Ao's mother was taken away a decade ago by unknown individuals. Naru Arata, Ao's 12-year-old childhood friend and the story's heroine, lives with her father, older sister, and grandmother.
She has a "Yuta" power awakened within her due to an incident when she was young. A mysterious entity called "Secret" suddenly appears and launches an attack on the Scub Coral lifeform on the island. Ao launches a certain military FP called "Nirvash" aboard a Japanese military transport in his fervent desire to protect the island.