Nanako Tenjō is a human character from the series who serves as the sniper for the terrorist organization CCC, operating under the code name 07 or Zero Seven. She was born on July 3, 1985. Her background is shaped by a traumatic event in her past that involved devils, which created an intense and deep-seated hatred for them. This trauma drives her primary motivation: a determined, single-minded goal to exterminate all devils. Her personality is marked by this strong resentment, and she is initially unwavering in her conviction that devils must be eliminated. She is portrayed as loyal, responsible, and hard-working in her role within the CCC, following her beliefs with a sense of duty.

In the story, Nanako Tenjō acts as an antagonist to the series' main characters, particularly Yuuki Anzai, a half-devil police officer, and his human partner Tsukasa Taira. Her role is that of a skilled operative who carries out the CCC's missions against devils, posing a direct threat to Anzai and those who seek coexistence. Her key relationships revolve around her fellow members of the CCC, with whom she shares the goal of eradicating devils. However, the most significant relationship that influences her development is her observation of Yuuki Anzai and Tsukasa Taira. As she witnesses their devoted relationship, which crosses the boundary between human and devil, her rigid thinking regarding the coexistence of humans and devils begins to change. This marks a notable character development, as she starts to question the absolute hatred that has driven her actions. Her notable ability is her exceptional skill as a sniper, making her a precise and dangerous asset for the CCC in their violent campaign.