Norio Koga is a supporting character in the Shadow Star Narutaru story. He is introduced as one of the missing passengers from the same plane flight as Shiina Tamai, and he later becomes the roommate and close friend of Takeo Tsurumaru. Norio has a distinctly feminine appearance, with long hair, earrings, and large eyes, which causes many other characters to mistake him for a woman. He is aloof and rude in his interactions with most people, and it is hinted on several occasions that he harbors a deep anger toward the human race. Despite this outward hostility, he possesses fierce loyalty toward Takeo, and over time he comes to tolerate and accept Shiina as well.

Norio is a Dragon Bearer who controls a high-level shadow dragon named Vagina Dentata, also referred to as Dentata or Bagi. His dragon takes an unusual form resembling a paper doll, reflecting Norio’s own artistic inclinations. He is skilled in crafting new shadow dragons as a hobby, and his ability to control his dragon is very high, placing him among the stronger bearers. He is also talented at modeling, often making dolls and holding exhibitions of his creations.

His deepest, most private wish is to have a child, and the name he gives his dragon is thought to reflect his longing for a woman who could give birth. This desire remains unfulfilled. Norio’s role in the story is primarily that of Takeo’s loyal companion and an ally to Shiina. He eventually moves in with Takeo and Shiina after her father’s aircraft is attacked a second time. His character arc is cut short by a brutal and tragic end: a gang of street thugs enters his and Takeo’s home, kidnaps Norio, and subjects him to torture, rape, and murder. His death deeply affects Takeo, who later avenges him by killing the perpetrators. Norio’s story underscores the series’ dark and unforgiving tone, as a character who, despite his bitterness and aloofness, had a hidden tenderness and a strong bond with those he trusted.