Midori Washio is a former elite member of the Kerberos unit, a heavily armed police tactical squad that was formed to combat crime in Tokyo but later disbanded due to its extreme methods. Alongside Kōichi Todome and Sōichirō Toribe, she formed a tightly bonded trio known as the Devil’s Trio. When Kerberos was ordered to disarm, the three refused and attempted to flee Japan by helicopter. During their escape, they were ambushed by bounty hunters, and Midori was gravely wounded. Despite her injuries, she and Toribe insisted that Todome leave alone, making him promise to return for them. This selfless decision highlights her loyalty and willingness to sacrifice herself for her comrades.

Midori is portrayed as a skilled combatant, proficient in using the squad’s heavy machine guns and powered Protect Gear exoskeleton. Her motivations are rooted in a deep sense of duty to her partners and a refusal to abandon the ideals they once fought for. Throughout the film, she exists largely as a memory and a haunting presence for Todome, who is tormented by his longing for her and the unresolved promise he made. A filmed confession of Midori is shown inside a movie theater, blurring the line between reality and Todome’s subjective experience. Her relationship with Todome was romantic, and his grief over her loss drives much of his psychological journey after returning to a surreal, decaying Tokyo.

Midori’s role in the story is essential as both a catalyst for Todome’s actions and a symbol of the past he cannot reclaim. She does not undergo further development in the film itself, as her fate is sealed early on, but her influence permeates the narrative, underscoring themes of sacrifice, memory, and the cost of idealism. Her notable abilities include combat expertise and tactical coordination, having been part of Kerberos’s elite core. Her personality, glimpsed only through brief scenes and recollections, is defined by determination, courage, and an emotional bond with Todome that transcends her physical absence.