Years have passed since humanity was brought to the brink of extinction by the sudden emergence of an unknown life form known as Gadoll. Those who survived live in Deca-Dence, a mobile fortress built to protect themselves from the Gadoll threat, situated at an altitude of 3,000 meters. The residents of Deca-Dence are divided into two groups: the Gears, who fight against the Gadolls daily, and the Tankers, who lack combat abilities. Natsume, a Tanker girl who dreams of becoming a Gear, meets the grumpy Kaburagi, who works as an armor repairman in Deca-Dence. This chance encounter between the seemingly opposite personalities of an optimistic girl who never gives up on her dreams and a realist who has left dreams behind will completely change the course of this world.
