Many years have passed since the abrupt advent of unknown life forms known as Gadoll brought humanity to the verge of annihilation. The survivors of this calamity now reside in the mobile fortress Deca-Dence, which is 3,000 meters high and was created solely to defend humanity from the Gadoll threat.
Three groups of people live in Deca-Dences: Gears and Warriors, who often battle the Gadoll, and Tankers, who lack the necessary skills. The somber Kaburagi, who was once a powerful warrior himself but is now simply an armor technician for Deca-Dence, meets Natsume, a young girl who lost her father and her right arm in a Gadoll attack and has dreamed of becoming a Gear ever since.
The outcome of this unexpected encounter between the optimist who never loses up on her goals and the realist who has long since left his behind may eventually define the direction this planet will take.
