Atsushi Kurase, an engineer for Helios Petrol, works aboard the Ocean Techno Polis, a technologically advanced floating city. When an unknown entity suddenly destroys the facility, his ex-wife and daughter are en route to visit him, driving his actions throughout the narrative. His engineering background provides crucial knowledge of the Ocean Techno Polis infrastructure. Following the disaster, he launches a desperate search to locate and rescue his family amidst the chaos and collapsing structure, a mission dictating his decisions.

During his search, Kurase faces obstruction from the Japanese navy, attempting to conceal classified military operations connected to the destruction. He uncovers these hidden activities while evading threats from naval personnel, persisting in his quest to reveal the truth behind the disaster and the military's involvement. The narrative depicts Kurase solely within the context of this immediate conflict: confronting military secrecy while pursuing his family's rescue in the disaster's aftermath.