In the year 2021, mankind was defeated by Gastrea, a parasitical virus, and is forced to live within a wall made of Varanium Monoliths, a metal that is able to subdue Gastrea. Soon, the "Cursed Children", children born with the Gastrea virus who are able to control it—which gives them superhuman abilities—were discovered. Due to the Gastrea virus' intervention, the Cursed Children could only be female. Civil Securities are formed to specialize in fighting against Gastrea, operating with the pair of an Initiator, who are cursed children, and a Promoter, serving to lead the cursed children. Ten years after the war, Rentarō Satomi, a high school student who is also a Promoter in his childhood friend Kisara Tendō's Tendō Civil Security, along with his Initator Enju Aihara, receives a secret mission to prevent the Tokyo Area's destruction.
Humanity has successfully colonized all the planets in the Solar System, with intentions to continue into new frontiers. Individuals live stable lives in these colonies, including young high school students living in 4th Tokyo on Mars. Two of these students are Iris Shirazaki and Mizuki Sera. Iris is finishing her last year of high school while studying to be a test pilot while her friend Mizuki also works as a mechanic on the aircraft. Her own brother, Kaito, oversees Mizuki and Iris as their homeroom teacher and program director.
Eleven years after the introduction of internet-connected, augmented reality eyeglasses and visors, Yoko Okonogi moves with her family to Daikoku City, the technological center of the emerging half-virtual world. Yoko joins her grandmother's "investigation agency" comprised of children equipped with virtual tools and powerful metatags. She quickly crosses paths with Yoko Amasawa, an expert hacker of the virtual environment, as Amasawa relentlessly seeks to "unlock" the mystery of a computer virus that emerges from an inaccessible corrupted space.
The Diclonius, a mutated homo sapien that is said to be selected by God and will eventually become the destruction of mankind, possesses two horns in their heads, and has a "sixth sense" which gives it telekinetic abilities. Due to this dangerous power, they have been captured and isolated in laboratories by the government. Lucy, a young and psychotic Diclonius, manages to break free of her confines and brutally murder most of the guards in the laboratory, only to get shot in the head as she makes her escape. She survives and manages to drift along to a beach, where two teenagers named Kouta and Yuka discovers her. Having lost her memories, she was named after the only thing that she can now say, "Nyuu," and the two allow her to stay at Kouta's home. However, it appears that the evil "Lucy" is not dead just yet...
Satoru Fujinuma is a struggling manga artist who has the ability to turn back time and prevent deaths. When his mother is killed he turns back time to solve the mystery, but ends up back in elementary school, just before the disappearance of his classmate Kayo.
In a far distant future, humanity has embraced the Fractale system as the ultimate path towards utopia. Comprised of several trillion networked computers, Fractale was created in the 22nd century to promote a peaceful lifestyle for the entire world in exchange of a periodic recovery of personal data from individuals through terminals located within their bodies. Living in a rocky coast region, Clain is a young boy fascinated by old technology. After helping a girl named Phryne, she gives him a pendant before disappearing by the next morning. Accessing the data from the peculiar gift, Clain ends up summoning a girl-shaped avatar named Nessa. Together they start a journey as they discover the truth behind the Fractale system.
Five girls live in 19th century London, a city within the Albion Kingdom divided into east and west by a large wall. The girls serve as undercover spies enrolled as students at the prestigious Queen's Mayfair school. The girls make use of their individual abilities to remain active in the underground world of disguise, espionage, infiltration, and car chases.
Set in the Shinigami technical school for weapon meisters, the series revolves around 3 groups of each a weapon meister and a human weapon. Trying to make the latter a "Death Scythe" and thus fit for use by the Shinigami, they must collect the souls of 99 evil humans and 1 witch.