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.
Two years ago, Shibuya was ravaged by a biological terrorist attack using the deadly Ua virus. Maria Osawa was saved when her father inoculated her against the virus, but is left with partial amnesia from the shock. She works as a cameraman when she reunites with a girl named Canaan in Shanghai, China. A gifted assassin with synesthesia, she is under orders from an unknown organization for a yet unspecified mission.
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.
Set in the year 2039, Japan is the under the rule of a multinational military force called GHQ after the country went into chaos due to the "Lost Christmas" incident ten years prior to the start of the series, when a giant outbreak of an alien virus called the Apocalypse Virus spreads during Christmas, causing the United Nations to send the GHQ to contain the outbreak and restore order. The series follows Shu Ouma, an intelligent yet socially awkward teenager who finds himself caught in the war between the GHQ and "Funeral Parlor (Undertakers)", a resistance organization led by Gai Tsutsugami, which aims to liberate Japan from the GHQ, when he meets Inori Yuzuriha, the famous Internet Singer of the band Egoist and a member of the Undertakers. Due to various circumstances, Shu acquires a genetic weapon called the Void Genome, also known as "power of kings", which allows him to extract "Voids", objects with special properties that reflect the personality of their owners from underage individuals. With his new powers, Shu joins the Undertakers to protect Inori and learns secrets and mysteries he never knew.
Takashi Komuro is a normal high school boy, until an infection breaks out that turns people into zombie-like creatures. Along with his friends & the school nurse, they fight their way out and continue their journey to find out what exactly has happened to the world.
On the island country Hinomoto, humans hide themselves in fortresses called "stations" against the threat of zombie-like beings with steel hearts known as "Kabane." Only armored locomotives known as "Hayajiro" go between the stations.
In a world where dead people turn into books and are stored in the Bantorra Library where anyone who reads a book can learn their past. Bantorra Library is maintained by Armed Librarians who wield psychic powers and their enemy is a religious society known as Sindeki Kyōdan.