In a dystopian near-future Japan, crime has spiraled so out of control that the Metropolitan Police form an elite heavily armored paramilitary unit known as the Kerberos Panzer Cops, or the Watchdogs of Hell. Equipped with machine guns and reinforced Protect Gear body armor, the unit successfully crushes urban chaos but becomes increasingly brutal and corrupt. When the government moves to disband Kerberos following public outcry, three of its top officers refuse the order. In the aftermath of a failed rebellion and a violent government crackdown, a desperate firefight ends with two of the trio, Midori Washio and Soichiro Toribe, gravely wounded. Their comrade, Koichi Todome, escapes alone via helicopter under a promise that he will one day return for them.

Three years later, Koichi, now a fugitive, secretly returns to Tokyo to find his lost comrades and uncover the truth. The city he once knew has transformed into a strange, decaying, and almost unrecognizable shadow of its former self. The film shifts into a surreal, dreamlike monochrome as Koichi, carrying a mysterious briefcase and hiding behind dark sunglasses, wanders this absurdist landscape. He discovers that even simple pleasures have been outlawed, such as the outdoor noodle stands that have been declared illegal gathering places for dissidents. As he searches, reality begins to unravel. He encounters a bizarre collection of characters, including a mysterious woman in red, eccentric con artists known as tachiguishi who specialize in elaborate dine-and-dash schemes, and an army of unsettling mime assassins.

The primary antagonist pursuing Koichi is the theatrical and menacing government investigator Bunmei Muroto. Muroto plays a surreal game of cat and mouse with the former Kerberos officer, subjecting him to absurd interrogations and relentless pursuit. As Koichi navigates this Kafkaesque nightmare, he is haunted by the ghosts of his past and struggles to distinguish friend from foe. The narrative builds toward a confrontation with his former allies, leading to a series of betrayals and rescues that blur the line between loyalty and survival. In the final revelation, the film pulls back to show that much of the surreal journey was a dying dream. Koichi was attacked and fatally wounded shortly after his return. The briefcase he guarded so fiercely does not contain his armor, but rather a pair of red spectacles. As his body is carried away, the mysterious woman in red observes quietly before walking off to find her next dream, leaving the true fate of the Kerberos legacy ambiguous.