Megarette, an 82-foot steel giant, crash-lands on the Earth after a long slumber in outer space. Anna, a young woman who is Megarette's alter-ego, finds herself lost and without memory on a future Earth that is back to its wild state. Who are those who have fished her from the waters of the lagoon and held her prisoner on a strange city-island? What is that enormous robot that looks like Megarette? The story will unveil Megarette's identity as well as Anna's past and destiny, while the shadow of an occult and devastating threat looms over the twilight of humanity.