Shuji and Chise are high school students who begin an awkward, tentative relationship after Chise gathers the courage to confess her feelings. Neither is naturally expressive — Chise is painfully shy and Shuji misses most cues — but the affection between them is real.
Then Sapporo is bombed in broad daylight by unknown aircraft. In the wreckage, Shuji finds Chise — but she has metal wings and weapons integrated directly into her body. Without her knowledge or consent, the Japan Self-Defense Forces have secretly transformed her into the nation's ultimate defensive weapon, its last line against what is coming. As Chise is deployed again and again and the invasions continue, the central question shifts: not whether Japan will survive, but whether the girl Shuji loves will survive the weapon she is slowly becoming.