Ken Kankei is the central protagonist of Tokyo Ghoul √A. He begins as a seemingly ordinary university student with a gentle and introverted nature, harboring a deep love for literature. This quiet demeanor, however, belies a tragic history; he lost his father at a young age, was raised by an overworked mother who later died, and subsequently endured a difficult childhood living with an aunt who resented him. His only solace was his friendship with Hideyoshi Nagachika, a cheerful and supportive peer who remained a constant link to his humanity.

In the narrative preceding Tokyo Ghoul √A, Ken’s life is irrevocably altered after a fateful encounter with Rize Kamishiro, a woman who is secretly a man-eating ghoul. Severely injured in her attack, he receives an emergency organ transplant from her, which inadvertently transforms him into a one-eyed ghoul, a hybrid being forced to subsist on human flesh to survive. Initially, he struggles to accept this new reality, working at the Anteiku coffee shop in the 20th ward, a haven for ghouls, and attempting to maintain his human identity. However, after being captured and subjected to a prolonged and sadistic torture session by the Aogiri Tree executive known as Jason, Ken undergoes a profound psychological break. This trauma awakens a ruthless and pragmatic side of his personality, symbolized by his hair turning stark white. His motivation shifts from passive survival to acquiring strength at any cost, believing he must become powerful enough to protect the few people he cares about, even if it means becoming a monster himself.

By the events of Tokyo Ghoul √A, Ken Kankei has transformed into a far more cold and calculating figure. He makes the controversial decision to leave the safety of Anteiku and infiltrate the violent Aogiri Tree organization, believing that by working from the inside he can better safeguard his former family from afar. His role in the story becomes one of a tragic anti-hero, whose well-intentioned but often misguided actions lead him down a path of isolation and conflict. His key relationships are defined by his distance; he shares a complex bond with Touka Kirishima, a fellow ghoul from Anteiku who cares for him but is deeply frustrated by his self-sacrificing and self-destructive choices. His friendship with Hide becomes a poignant thread as his childhood friend attempts to reach the person Ken used to be.

Throughout √A, Ken’s development is marked by his internal struggle to control his growing power and his descent into a perceived state of necessary cruelty. He cannibalizes other ghouls to become stronger, developing an unstable kakuja, a powerful but mentally corrosive mutation of his predatory organ called a kagune. His notable abilities, inherited from Rize, include a potent Rinkaku-type kagune, which manifests as several scaled, tentacle-like appendages from his lower back. After his torture and subsequent cannibalism, his kagune can take on a monstrous, centipede-like form that grants him immense strength and regeneration but also threatens to consume his sanity. Ultimately, his journey in this season culminates in a desperate confrontation with the CCG, the human agency that hunts ghouls, where he finally reunites with Hide in a tragic conclusion that forces him to confront the ultimate cost of his power and choices.