In a near-future Tokyo City where money and violence dictate the rhythm of the night, a small detective agency called Night Owl operates on a simple principle: accept any request, provided the price is right. At its center is Sumeragi Sento, a brilliant but deeply peculiar detective who is a crybaby, physically weak, and afflicted with severe germaphobia due to a traumatic childhood. Sento possesses a unique and taxing ability known as mind reading, allowing him to hear the hidden thoughts of anyone he faces directly. This power, however, is not absolute; it strains his mind and can be deceived by individuals who truly believe their own lies.

Assisting him are a pair of enigmatic twin recorders, Hoshibami Mete and Hoshibami Yunde. The twins, who share a dark past involving an abusive father, provide a stark contrast to Sento. Mete is the calmer, more analytical brother, while Yunde is impulsive and direct, often teasing their fastidious boss. Together, the three of them make up the rank 50 detective office within the unified detective organization known as the Nest.

The story unfolds through a series of complex and grisly cases that pull Night Owl deep into the city's underworld. Their first major case involves a girl whose organs have been stolen, leading them to a cursed girl at the heart of a series of high school girl murders. Sento and the twins must unravel the emotional and physical bonds tying the victims together. The narrative then escalates into a conflict with the three major gangs that control the city: Vincent and Eve, whose rivalry threatens to ignite a full-scale turf war after the murder of a top dancer named Reiza Julia. Night Owl, drawn into the investigation, must navigate the intricate web of gang politics, calling upon a third faction, Violetta, to act as a mediator in a desperate attempt to maintain the city's fragile balance. As the layers of deception are peeled back, the true culprit behind the escalating violence is finally exposed, leading to a confrontation that forces one of the key players, Shiimi Saria, to face her own end. The series concludes as the Owl, having navigated a landscape of greed, violence, and betrayal, finally consumes its last rat in the night.