A 20-year-old man living in the underground cell of a pharmaceutical company, unmarried. He works for the Black Organization, his daily routine consisting of physical examinations, taking medicine, and returning to his cell. One day, a female colleague, his superior known as Sherry, arrives at his workplace. As a time traveler, he should befriend her, but he just wants a peaceful life... A mission is issued by a system called the Devil System, and he begins a life destined to be anything but peaceful.