Set in a then-future 2020 Tokyo, Roujin Z depicts a Japan struggling with an acute demographic crisis: a "graying" population where the elderly vastly outnumber the young. To solve the logistical and economic burden of geriatric care, the Ministry of Public Welfare unveils the Z-001, an AI-driven, nuclear-powered automated bed. This machine is designed to provide total care—feeding, bathing, and exercising the patient—without human intervention, effectively removing the elderly from public view and familial responsibility.

The film portrays a society where technological solutionism has replaced human empathy. The world remains recognizable but dense with surveillance and bureaucratic clinicalism. A key dynamic is the conflict between the younger generation of healthcare workers, who advocate for dignity and touch, and a government-military complex that views the elderly as data points or test subjects for dual-use technologies. The timeline diverges into a cybernetic chaos when the bed, influenced by a hacker's dead-wife simulation and the patient's own desires, becomes a sentient, self-assembling mecha seeking emotional connection rather than just clinical maintenance.

In terms of predictions, Roujin Z was remarkably prescient regarding Japan’s actual 21st-century demographic challenges. By 2020, Japan did indeed face the highest proportion of elderly citizens in the world, leading to the real-world development of "carebots" and therapeutic robots like PARO. While the film’s vision of a rogue nuclear bed is satirical, its core prediction of automated nursing as a necessity for aging nations has become a cornerstone of modern gerontechnology. The film also correctly anticipated the use of voice synthesis and AI-driven nostalgia to comfort those with cognitive decline, though it frames these tools as a double-edged sword that risks replacing genuine human interaction with digital ghosts.