When a cutting-edge virtual reality medium called D Movie sweeps Japan in the early 1980s, troubled youth begin abandoning their physical forms to inhabit these digital worlds indefinitely, leaving their bodies to deteriorate in the real world. To combat this crisis, the government establishes Diamond Dog, a specialized agency tasked with retrieving these "Sinkers" through agents called Debuggers who venture into the virtual realm themselves. When seventeen-year-old Yūki Sayaka becomes trapped in a D Movie called "Story of the Ruined Capital" and remains undiscovered for three days, her fragile health makes her situation dire—she has less than a day before she may slip away permanently. Debuggers Shijima Ryō and Tobari Maria are sent into the virtual world on a desperate rescue mission, racing against time to pull her back before it's too late.