Tokyo Ghoul is set in an alternate reality where ghouls, individuals who can only survive by eating human flesh, live among the normal humans in secret, hiding their true nature to evade pursuit from the authorities. Including enhanced speed and senses, a regular ghoul is several times stronger than a normal human and have at least one special predatory organ called a “Kagune”, which they can manifest and use as a weapon during combat. Another distinctive trait of a ghoul is that when they are excited, the color of their sclera of both eyes turning black and their irises red, or in only one eye in the case of a half-ghoul. A half-ghoul can either be born naturally as a ghoul and a human’s offspring, or artificially created by transplanting some ghoul organs into a human. In both cases, a half-ghoul is usually much stronger than a pure-blood ghoul.
The story follows Ken Kaneki, a college student who barely survives a deadly encounter with Rize Kamishiro, his date who reveals herself as a ghoul, and is taken to the hospital in critical condition. After recovering, Kaneki discovers that somehow he underwent a surgery that transformed him into a half-ghoul by transferring some of Rize’s organs into his body, as she died when she attacked him, and just like them, he must consume human flesh to survive as well. With no one else to turn to, he is taken in by the ghouls who manage the coffee shop “Anteiku”, who teach him to deal with his new life as a half-human/half-ghoul, including interacting with ghoul society and its conflicting factions, while striving to keep his identity secret from other humans.
The prequel series Tokyo Ghoul: JACK follows the youths of Kishō Arima and Taishi Fura, two characters from the main series who become acquainted when they join forces to investigate the death of Taishi’s friend by the hands of a ghoul, leading to Taishi eventually following Arima’s path and joining the CCG (Commission of Counter Ghoul), the federal agency tasked into dealing with crimes related to ghouls as well.
The sequel series Tokyo Ghoul:re follows an amnesiac Kaneki under the new identity of Haise Sasaki, the leader of a special team of CCG investigators called “Quinx Squad”, that underwent a similar procedure as his, allowing them to obtain the special abilities of Ghouls in order to fight them, but still being able to live as normal humans.