Kouzou Karino is a lieutenant in the Tokyo Police Department's specialized 'U' Division, investigating unusual and supernatural cases. He regularly partners with Ayaka Kisaragi's paranormal investigation agency, acting as her primary police contact by sharing case details and crucial clues. Dedicated to his duties, his practical effectiveness is sometimes hampered, such as by poor marksmanship during field operations.

Karino harbors a consistent romantic interest in Ayaka, frequently trying to protect her from supernatural dangers and her own self-destructive tendencies like heavy drinking and impulsive spending. His attempts to show affection, such as offering pastries, often result in mishaps. He undertakes personal surveillance of suspects to aid her work, though his unreliable Volkswagen Beetle frequently breaks down at critical moments, complicating these efforts.

During investigations, he exhibits courage despite physical vulnerability. While independently probing the fraudulent Hadja monks, he was captured and subjected to life-threatening retaliation, including being dangled over a pit of vengeful spirits as punishment for exposing their schemes. These incidents underscore his persistence despite limited combat capabilities.

Subtle developments mark the progression of his relationship with Ayaka. By the OVA series' conclusion, mutual romantic tension surfaces, culminating in a near-confession of feelings during a vulnerable moment. Their associates quietly observe this interaction, signaling a significant yet unresolved shift in their dynamic.