Koichi Doi develops specialized space food as a food formulation researcher for Defy Foods, aiming to preserve astronaut bone mass on the International Space Station. When fellow astronaut Orudo Noguchi, suffering space radiation exposure, entrusts Koichi with delivering a birthday package to his Earth-bound daughter Monaka, Koichi accepts. Subsequent medical evaluations reveal Noguchi and another crew member are experiencing abnormal bone volume increases. The onboard doctor traces this to an interaction between space radiation and Koichi's food formulations, which bypassed full lab testing. This triggers a grotesque mutation, transforming the affected men into homicidal, bulletproof monsters. These creatures kill most crew and security personnel before survivors destroy the station to eliminate one monster; the other escapes. Koichi evacuates with the doctor and remaining crew.

Post-disaster, Defy Foods dispatches agents to contain the incident and eliminate reputation-threatening evidence. Koichi participates, helping silence witnesses and hunt the escaped monster. He arrives during a confrontation between the monster and Monaka Noguchi, who operates as the vigilante "Angel of Death." Koichi witnesses the monster's defeat and recognizes Monaka. He and the agents take her to an isolated parking garage for debriefing, where she learns the monster was her mutated father. When the agents attempt to kill Monaka, she eliminates them. Koichi then tries to manipulate her, expressing sympathy and urging cooperation. This attempt fails, and Monaka executes him.