Naru Ōtori is a cheerful, genki high school student, often appearing airheaded yet revealing surprising perceptiveness in social dynamics. As the younger sister of Kakeru Ōtori, leader of the Yanagihara Flame Birds gang, she connects to the story's street-level conflicts. Her central relationship with antisocial handyman Hayato Narita begins when she hires him to find her missing bicycle. She develops a romantic interest in Hayato, actively pursuing him, displaying jealousy toward rivals like Martinez, and exhibiting a recurring fetish for worker uniforms. Her involvement persistently extends into Hayato's nocturnal world alongside gang affiliates, transitioning her from client to an integral part of his social sphere.

This connection to the underworld, primarily through her brother Kakeru, places Naru in perilous situations, including a life-threatening café confrontation where violence results in a close-call haircut. Her cheerful nature provides emotional grounding for Hayato, catalyzing his gradual openness to human connection despite his antisocial tendencies. The initial bicycle search evolves into broader involvement with street conflicts, gang disputes, and revelations concerning personality fragmentation among protagonists. Familial ties make Naru a bridge between ordinary life and criminal elements, a role underscored when her brother's split personality, the unhinged "Phoenix," experiences personality bleed-through events with Hayato. Naru's unwavering positivity endures through witnessing violence and the psychological unraveling of central characters.