Mariko Shiratori, a 24-year-old news reporter and anchor for GUIL-TV, secured the coveted main anchor position on the station's signature "Prime Time News" during only her second year with the news department. A graduate of a British university, she presents an intelligent and beautiful appearance. Her demeanor blends nobility with attentive femininity and gentleness, yet she possesses a strong inner conviction against wrongdoing. Initially, she has very limited sexual experience and is a virgin.

Unbeknownst to the public, GUIL-TV is infiltrated by a mafia organization running an underground prostitution ring. Directors exploit newscasters, idols, and actresses as sex slaves, training them as high-class prostitutes to enhance their on-air appeal. Following producer Shunsuke Haruna's transfer, Akira Okazaki—recently released from hospital after lengthy treatment—becomes Mariko's producer. Upon Okazaki's return, Mariko reacts with full-body trembling due to intense nervousness, having previously become his obedient sex slave. She immediately resumes her submissive role, addressing him as "Master." Within GUIL-TV's secret organization, Okazaki personally trains Mariko, while other staff train additional women like idol Kaori Yukimura.

Mariko maintains a distant relationship with her colleague, 26-year-old senior newscaster Saeko Kajio, who temporarily substitutes for her on "Prime Time News." Mariko interprets Saeko's behavior as jealousy over her primary anchor role. Meanwhile, 21-year-old rookie newscaster Yumi Shimura, an assistant anchor on the same program, holds deep admiration for Mariko, viewing her with near-romantic intensity. Yumi's awareness of these feelings intensifies after witnessing Mariko being subjected to degrading acts.