A colossal steel being descends from the heavens, leaving a path of destruction across the land. Humanity is powerless against this metal marauder, unable to stop its relentless advance. The story is set in a world where science fiction and ancient mythology collide, unfolding almost entirely without dialogue or text, driven instead by powerful, page-filling artwork.

The narrative centers on two primary forces. The first is the unknown invader, a giant robot or mecha that arrives from space as a harbinger of ruin. The second is a young girl, a priestess living deep in the mountains, who becomes humanity's unlikely hope. When she learns of the devastation, she performs an ancient ritual tied to the patron goddess of ironmaking. This act of resolve awakens a massive mecha of her own, which she either pilots or becomes one with, leaving the interpretation open to the reader.

The plot follows the confrontation that erupts from this awakening, blending elements of a sci-fi fairy tale with the spectacle of classic giant robot conflicts. The core narrative arcs include the Advent, the descent of the destructive steel visitor and its initial attack; the Ritual, where the young priestess discovers the threat and performs her ancient ceremony to summon or become a protector; and the Duel, a wordless battle between the two colossal beings. The story concludes abruptly but without feeling incomplete, focusing on the awe and scale of the conflict rather than an extended resolution.

The manga pays homage to the giant robot anime and manga that the creator grew up with, and it draws loose inspiration from the myth of Kanayago-kami, the patron goddess of the traditional Japanese tatara ironmaking method.