Kozo Karino is a police lieutenant working in Tokyo's Shinjuku district. His duties involve investigating cases with suspected supernatural elements, leading him to frequently collaborate with Ayaka Kisaragi's paranormal investigation agency. He is characterized as somewhat clumsy professionally.

He appears across multiple agency cases. During the investigation into mysterious deaths at Asama Hospital, he independently pursued the case, crossing paths with Ayaka and her team. This investigation uncovered a poltergeist possessing the hospital director and causing fatal accidents to harvest organs. Later, during an incident at the Nakasugi Department Store involving a cursed archaeological exhibit, he supported Ayaka's efforts to resolve supernatural disturbances. His most significant involvement occurred confronting the esoteric Buddhist group Hadja, which orchestrated artificial monster plagues across Tokyo. Probing Hadja's activities led to his capture, requiring rescue by Ayaka and her team. This culminated in a confrontation where he intervened to assist Ayaka during her rooftop battle against the group's leader.

His professional relationship with Ayaka shows indications of potential romantic development, particularly evident when he actively assists her during critical moments, including her rescue. This aspect of their dynamic was intended for further exploration had the series continued.