More than two centuries have passed since Japan was devastated by nuclear war. Cut off from the world, the island is now a place of terror and mysteries: wonders of science some believe best forgotten, monuments to a bygone era of human decadence, and irradiated monsters ready to tear apart any humans foolish enough to set foot there.

After being wrenched from his family and falsely convicted, a French soldier of fortune named Leon finds himself on a cargo plane to Japan. He and his fellow convicts are given one year to locate a powerful weapon from ages past-a weapon known only by the codename TORATSUGUMI-in exchange for their freedom. But what is the true nature of this weapon, and how is it connected to the taloned, half-human girl who swoops in to save Leon?