As humanity hurtled toward extinction, they were also threatened by the emergence of life forms known as Gadoll, which caused the destruction of 90% of the world's population.

The company created a giant dome on the Eurasian continent in which they installed a colossal entertainment facility called Deca-dence, with its own independent all-governing system to make all decisions.

In the fortress city of Deca-dence, the lowly Tanker girl, Natsume, dreams of becoming a Gear warrior following her father's death during a Gadoll attack.

[9] Director Yuzuru Tachikawa and chief producer Takuya Tsunoki, who had joined Madhouse around the same time and collaborated on the 2015 series Death Parade, had talked about creating their own original work.

[10] Writer Hiroshi Seko, who had previously worked with Tachikawa on Mob Psycho 100,[7] was eventually added to the project after some foundations had been built and, together, the four created the series' original concepts.

[12] While the production team decided to have a world view of "fighting against big monsters", they wanted to add a plot twist on top of it.

The staff found Oshiyama's design of mechas to be organic and soft, yet still clearly mecha-like, which suited Deca-Dence, and therefore invited him to join the project.

[18] Christopher Farris of Anime News Network gave the final episode a score of 3 out 5 stars, concluding that the producers "didn't come down as definitively as they could with an alternative to that accursed capitalism, or manage to wrap everything with satisfyingly-tied emotional bows.