High school student Ibuki Keita has been haunted by misfortune for as long as he can remember. For no apparent reason, everyone around him dies tragically. Ultimately, he refuses to become too close to anyone, even his childhood friend Akane. This leaves Keita alone in a life full of misery and disgrace. While eating at his favorite ramen shop one evening, Keita meets a strange young girl named Kuro. Possessing abilities that surpass that of a normal human being, Kuro classifies herself as a Mototsumitama. She explains to Keita about "Terra," a life-energy force split between three identical looking people; a global phenomenon dubbed the "Doppeliner System." As a Mototsumitama, Kuro guards the "Coexistence Equilibrium," the beings that protect the flow of Terra around the world. Keita refuses to believe her story, until he is caught up in the crossfire of this hidden world. On the verge of death, he makes a contract with Kuro, unbeknownst to its true meaning. Now he is bound to Kuro, and must be with her at all times. Could Keita's misfortune possibly get any greater?

Vampires—supernatural beings that feed on the life essence of the unsuspecting at night—have been around for centuries. However, high schooler Karin Maaka is unusual, even among her own kind. Unlike her vampire family, ever since she was a child, Karin has suffered from polycythemia: a rare disorder which causes her to periodically produce excessive amounts of blood. And the more blood she produces, the more anemic and lightheaded she gets, ultimately leading to frequent nosebleeds. Her only solution? Force her excess blood onto random strangers, which surprisingly causes these "victims" to become livelier and happier than before. With her siblings—Anju, her reserved yet affectionate younger sister, and Ren, her womanizing elder brother—helping her abilities remain a secret by altering the affected humans' memories, no one is the wiser. That is, until Karin's newly transferred classmate, Kenta Usui, finds her behavior suspicious. And to make matters even more complicated, Karin feels her blood reacting unusually to Kenta's presence.

In the city of Judoh, Claire Leonelli has inherited leadership of the Mafia group "Vampire" following the death of his father. To keep Claire's and other criminal activities in check, the city's Bureau of Urban Safety has Special Services Division operative Daisuke Aurora and the super android codenamed "J" (whose identity is apparently kept in secrecy, as androids are banned in the city). With both of them around, crime now has little room to breathe in Judoh. (Source: ANN)

Corruption looms over the prosperous Russell City, where manifestations of negative emotions called Horrors cause chaos and mayhem. The Makai Order is the last bastion of hope against these unholy creatures. Using several small businesses as fronts, they deploy powerful Makai Knights and magical Makai Alchemists to combat the Horror threat. Within this secretive order, the highest rank of Golden Knight has been bestowed upon a large, powerful man named Sword, granting him use of the Garo armor and blade. He alone knows of a plot that threatens the entire Makai Order, with his only hint being the phrase “El Dorado." While fighting a Horror, he encounters Sophia "Sophie" Hennis, a teenage girl whose brother's disappearance years ago is also linked to the same phrase. The two agree to work together to uncover the truth behind "El Dorado" and the disappearance of Sophie's brother. [Written by MAL Rewrite]