Akira, a member of the Earth Defense Force EGT, is secretly Lucia, an alien from the G55 galaxy. As part of an interstellar patrol force, he actively fights against vicious monsters and hostile aliens to protect Earth, constantly battling to ensure the planet's safety. However, Mara, a female alien aiming to conquer Earth, targets Lucia for destruction and sends the giant robot Dekaizer near an oil refinery complex. Heavily armored, Dekaizer overwhelms Lucia during their seaside battle, putting him in a tough struggle—yet Lucia barely manages to claim victory. Immediately afterward, Lucia is enveloped by a black fog and teleported to a mountainous region, bound with crosses affixed to his body.