Chikyuu Bouei Kigyou Dai-Guard

The 21st Century Security Corporation is tasked with defending against the Heterodyne, an alien species that reappeared after a 13-year absence. To counter this threat, the company's office workers operate Dai-Guard, a massive robot previously considered a relic. Although Dai-Guard is outdated and requires maintenance, its operators face the challenge of protecting the world from the Heterodyne menace.