The Anime Lad
Humanity survives inside Deca-dence, a three-thousand-meter mobile fortress built against the Gadoll threat. Natsume is a Tanker who dreams of becoming one of the Gears fighting outside. She meets Kaburagi, an armor repairman who has given up on his own dream. His quiet routine is now in danger.
Gigguku
Deca-dence is a three-thousand-meter fortress carrying the remains of humanity while warriors fight Gadoll outside! Natsume refuses to surrender her dream of joining them. Then she meets Kaburagi, an armor repairman who has abandoned his own dream, and their opposite energies hit like a collision.
Father's Basement
The post-apocalyptic fortress and weary repairman are recognizable parts, and the opening premise has plenty to explain. Natsume gives it forward pressure. She is a Tanker determined to become a Gear, while Kaburagi has stopped believing in dreams at all. Their chance meeting puts the contrast to work.