The series is set in Zentrix City, a seemingly perfect city. Emperor Jarad is a scientist who with the help of scientists Dr. Roark and Dr. Coy, created a super-computer called OmnicronPsy, which manages all of the city's higher and day-to-day functions, controlling a wide variety of machines and robots, allowing humankind to live a seemingly perfect life. However OmnicronPsy, using His super-intelligence, decides that it would make a better ruler than Jarad, and starts to break down the coding that stops him from revolting and harming the Royal Family. Discovering this, Jarad and Dr. Roark head back in time 7 years to stop the revolt from ever happening. To accomplish this they plan to shut down the six Zentrium chips that power OmnicronPsy. Upon discovering this, Jarad's daughter and only heir, Princess Megan, proceeds to follow him to the past while OmnicronPsy concurrently undoes his restriction codes and sends his Robo Guards to hunt her down.

Sentenced to death, ninja Gabimaru the Hollow finds himself apathetic. After leading a blood-soaked life, Gabimaru believes he deserves to die. However, every attempt to execute him inexplicably fails. Finally, Sagiri Yamada Asaemon, a fledgling member of a famed executioner clan, is asked to take Gabimaru's life; yet Sagiri makes no move to kill him as requested. Insisting that Gabimaru will not die because of his love for his wife, Sagiri instead offers him the chance to obtain a full pardon for his crimes. If he can travel to the island of Shinsekyo and obtain the Elixir of Life—which supposedly grants immortality—and bring it back for the shogun, then his freedom will be assured. But of the many who have traveled to Shinsekyo in search of the mythical Elixir, not a single person has returned sound of mind, if at all. Though unaware of the numerous dangers ahead, Gabimaru decides to accept the offer—alongside ten other death row convicts—in hope that he and his wife may finally live in peace.

Akane Nishimura's quiet nature makes her classmates perceive her as a gloomy and unlikeable person. Combined with her intimidating gaze, it earns Akane the ominous nickname Grim Reaper, condemning her to endless bullying for her supposed cursed powers that bring misfortune to everyone around her. However, none of these rumors deter transfer student Taiyou Takada from trying to befriend Akane. As someone who finds the supernatural fascinating, Taiyou approaches the Grim Reaper without hesitation, blissfully unaware of the complicated situation within the class. His bright personality and optimistic worldview may just bring about the change that Akane desperately needs.

Ai Enma and her companions continue to offer their service of revenge against those who have wronged others, and the price is as steep as ever—for damning the offender to hell, the person exacting vengeance is sent to the abyss as well. As they cast soul after soul into the darkness, a new sinister force is watching them: a little girl named Kikuri. While Ai continues her duties, she meets a boy named Takuma Kurebayashi, known as the Devil's Child because of the horrific events that occur around him. Unfortunately, Takuma's reputation leads the townspeople to use him as a scapegoat for those who have been ferried off to hell. When things quickly spiral out of control, Ai must find a way to bring an end to this senseless violence, as it poses a threat to her very existence.