A paranormal researcher and the handsome 17 year-old president of the SPR, Shibuya Psychic Research. His nickname "Naru" is short for "narcissist", given to him by Mai.
Contrary to the other characters, he does not appear to possess any kind of spiritual power, and must count on his companions' abilities and his own intellect and knowledge to solve the cases they investigate. It is later revealed that Naru is an extremely powerful psychic, but using it takes a toll on his body because it is difficult to control and can only be used as raw power.
Though appearing cold and critical in front of his friends, he does care for them deeply and has earned their trust and respect. He and Mai apparently share a close relationship as she is the only girl he addresses by given name, unlike Ayako (Matsuzaki-san) and Masako (Hara-san), resulting in the latter becoming jealous of Mai. When Mai notices that Naru treats her differently from their friends, she becomes angry and confronts him; Naru only smiles to indicate she is special to him. It is hinted he likes Mai romantically throughout the story.
In the novels, it is revealed that Naru's true name is not Kazuya Shibuya and that he is the famed paranormal researcher, Oliver Davis. Naru had a twin brother named Eugene; they were nicknamed Gene and Noll (Naru). Naru's true identity as Oliver Davis is only known to Masako, as she had seen him in a video performing PK before they met, and uses this knowledge as leverage over him. When Mai first addresses him as Naru, he is shocked and asks how she knows the name because the Japanese pronunciation of Noll sounds identical to Naru, but she quickly explains it is because of his narcissism, ending his concern. Both Naru and his brother were orphans and were later adopted by the Davises. Naru actually went to Japan to search for his deceased brother whose death he experienced through psychometry; Gene was run over by a car and later thrown into a lake to destroy any evidence of the accident by a woman whose identity is still unknown. It is later revealed that Naru cannot use his ability without physically injuring himself, since Gene's powers normally would have prevented such injuries; therefore Naru was taught by Lin to control it. When Naru left for England after finding Gene at the end of the Evil Spirit series, Mai confesses that she likes him. At this, he asked her if she likes him or Gene. He claims that the one she likes is Gene, who appears in her dreams and not him. Naru went back to Japan (together with Lin) two months after Gene's funeral stating that there is more supernatural activity there.
Also the novels reveals that the company named SPR, allegedly "Shibuya Psychic Research" at Dogenzaka, Shibuya, is actually a branch company for the Society for Psychical Research (also called SPR) and that the C.E.O is Naru's adoptive father, Martin Davis.