Live action TV
Description
Kengo is the owner of a tattoo parlor called KOYA, which functions as a neutral territory and a truce zone for the three rival gangs that fight for control of the virtual Shibuya. His establishment serves as a rare place of safety and respite, where characters such as Tsuyoshi, Asagi, and Ema can eat, rest, and recover from their injuries, often working off debts in exchange for his hospitality. Kengo is a tall figure, standing at 6 feet 1 inch, and his demeanor is often described as affably evil, maintaining a calm and reasonable exterior even while overseeing a system designed to trap and reset teenagers.

Beneath his role as a neutral shopkeeper lies a far more significant function within the world of Sh15uya. He is the one who controls and watches over the city from behind the scenes, acting as an administrator for the virtual simulation. In the real world, Kengo is revealed to be the teacher of the classroom where the fifteen-year-old participants are physically located, making him directly responsible for overseeing their experience within the educational system. He refers to the virtual Shibuya as a perfect educational system, where gang conflicts are a kind of athletic meet designed to help troubled teenagers grow stronger by facing challenges. In this capacity, he serves as a mole in charge, answerable to a superior named Igaya, the chairman of the project.

Kengo's motivations are rooted in the function of the system he helps to maintain. He initially believes in the purpose of the simulation as a means of correcting the behavior of problematic youths, overseeing the cycles of conflict, death, and reset that define life in Shibuya. He is the one who dispatches Piece, the assassin that marks and kills broken individuals who exceed the world's limitations, and later sends armies of robots to enforce the system's rules. Despite his authoritative role, he possesses standards and is not purely malevolent. Seeing his boss, Chairman Igaya, for what he truly is becomes the catalyst for a heel-face turn, leading Kengo to ultimately help the main characters escape the virtual world.

Throughout the story, Kengo's key relationships evolve significantly. He maintains a professional distance from most inhabitants, viewing them as students within his charge. He provides shelter and information to Tsuyoshi and Ema, the two protagonists who can remember those who have been reset, while also posing a major obstacle as the story's overseer. His position places him in direct conflict with their goal of escape, yet by the end of the series, he joins Tsuyoshi, Asagi, Ryuugo, and DJ in preparing to leave Shibuya, completing his transformation from antagonist to ally. Notably, his actions as the dragon of the system are easily forgiven and immediately forgotten after the Shibuya 15 regain their real memories.

In terms of abilities and authority, Kengo does not possess overt superhuman powers but instead has immense control over the virtual environment. He commands Piece, the deadly enforcer of the system, and can summon numerous mechanical robots to serve as his agents. His authority is such that he can punish those who challenge him, such as when he marks Ema and sends Piece after her for discovering his secret. As the teacher in the real-world academy, he knows the true identities and seat numbers of all the participants, revealing to Tsuyoshi that he is seat number twenty-one, Tsuyoshi Mamiya. His position as the gatekeeper of the simulation makes him one of the most powerful figures within the narrative.