Kunai, also known as Kudo Naito, is a founding member of the artist collective DoRed and Ran Akagi's right-hand man. The two have been close friends since childhood. Abandoning graffiti ambitions, Kunai discovered a greater aptitude for technology, developing exceptional hacking skills that fuel DoRed's operations.

Driven to improve Shantytown and aid his grandmother, Kunai created an app monitoring brain waves and vital signs for health feedback. External forces exploited his well-intentioned technology, transforming it into "Drug D"—an addictive, euphoric experience masquerading as an illegal substance. This corruption coincided with a redevelopment scheme targeting Shantytown.

Discovering the misuse, Kunai planned a terrorist attack on Howard Win's yacht to expose the Drug D conspiracy and redevelopment plans. Authorities orchestrated his public assassination by SARG operatives while Ran watched, intending to justify increased surveillance. Kunai's death fractures Ran's bond with Koki Suido and ignites resistance against the ward's leadership.

Before his death, Kunai publicly exposed the truth about Drug D and the redevelopment scheme through broadcasts and social media. This disclosure compels Mayor Gori Suido to confront the fallout and shapes subsequent events involving the KANAE surveillance system, highlighting themes of technological ethics and systemic oppression.