Beyond ordinary Tokyo lies the Black World, a parallel realm where supernatural demons dwell. For centuries, a fragile peace treaty has kept the two worlds in relative balance, guarded by a covert force known as the Black Guard, a group that also fights back against radicalized sleepers from the Black World who seek to upend the agreement. The narrative follows a man who walks between duties and danger, balancing a mundane daytime life with the nocturnal demands of protection and sacrifice.
Renzaburō Taki is an electronics company salaryman by day and a Black Guard operative when the night calls. His personal life collides with the mission when he begins a clandestine affair with Kanako, a young woman he’s been meeting at a bar for several months. Kanako reveals herself to be a spider-like doppelgänger from the Black World Radicals and escapes after trying to kill him, leaving behind a sample of Taki’s semen as part of a disturbing encounter that foreshadows the peril he faces. The next day, he’s assigned to protect Giuseppe Mayart, a dwarfish, two-hundred-year-old mystic who is both peculiar and powerful, and a signatory of the treaty. Mayart’s protection has become Taki’s new priority, and he learns he will be working alongside a partner from the Black Guard, a collaboration that will put his loyalties to the test.
As the three assemble, they head toward Narita to welcome Mayart, only to be ambushed by two Radicals on the runway. They’re saved at the last moment by a striking partner: Makie, a beautiful fashion model who is also a Black Guard member. The trio eventually makes their way to a Hibiya hotel that stands as a sanctuary built with spiritual barriers designed to shield them from Radicals’ intrusions. While they pass the time with a quiet game of chess, the hotel’s history and purpose are explained by the hotelier, an elder figure who underscores Taki’s uncertainty about his role. This moment hints at a bigger truth: Taki must learn what he is protecting before he can truly value his position within the Black Guard. The sense of looming danger intensifies when a Radical named Jin orchestrates an assault, forcing Mayart to slip away.
Makie and Taki locate Mayart in a soapland, where a Radical has exploited his frail health, and they rush him toward a spiritual hospital shielded by Black Guard protection. Midway, Makie is captured by a tentacled demon, and Taki is compelled to press onward without her. At the clinic, Mayart begins to recover, but Shadow—the radical leader—appears in a psychic projection to taunt Taki about rescuing Makie. Despite Mayart’s warnings that he could lose his job, Taki chooses to pursue Shadow to a ruined building far from the hospital, where he discovers Makie in danger, her vitality sapped as Radicals torment her. He defeats the other aggressors and wounds Shadow, barely escaping.
In the aftermath, Makie reveals a deeper connection to the conflict: she once loved a member of the Radicals and joined the Black Guard because she believes in forging peace between the two worlds. Returning to the clinic, the couple finds themselves dismissed by their superior, who views their bond as a liability to their duties. The situation becomes even more perilous when a tunnel stowaway Mayart is involved in their flight, and Kanako resurfaces with renewed resolve to kill them, determined to sever their genetic link. Supernatural lightning erupts, killing Kanako and leaving Taki and Makie wounded, but alive. They awaken in a church and share a moment of intimate connection that redefines their alliance.
A renewed assault from Shadow follows, but Mayart—who remains unexpectedly healthy—channels a surge of lightning that shifts the odds. In a dramatic turn, Makie’s powers deepen after she becomes pregnant with Taki’s child, and she delivers the decisive strike that breaks Shadow’s hold. Mayart reveals the larger purpose behind their mission: Taki and Makie, as a couple bridging human and demon bloodlines, are essential to a new peace treaty. They are chosen to be the first cross-species pair capable of bearing half-human, half-demon children—an enduring symbol of harmony for both worlds. Although initially angered by the hidden agenda of the Black Guard, Taki accepts the path before them and, embracing the hotelier’s counsel, vows to protect Makie and their future child. With a sense of resolve, the trio heads toward the peace ceremony, and Taki decides to remain with the Black Guard to safeguard both worlds—and the people he loves.
