Rookie detective Saki and her partner, veteran detective Hirai, are in charge of a case involving the confinement and rape of young women. The only clue is a toy necklace left at the scene. They also discover that the victims share the same date of birth. A former rapist then comes into the picture, but...

Chief Saki of the Sex Crimes Investigation Division. The Sex Crimes Investigation Division was specially established to tackle sex crimes occurring day and night. At times, Chief Saki herself conducts undercover operations using her own body. Tsuchiya, the boss of the First Investigative Division, disapproves of this. He constantly obstructs Saki, yet orders her to work alongside a female investigator dispatched from the Hong Kong Police

Saki is a detective in the Sexual Crimes Investigation Division. She works alone with her boss, Iwasaki, in a so-called dead-end department. Just then, her boyfriend, Taiki, emerges as a key witness in a rape case. The victim is Rie, a medical student and Taiki's student. She was raped by a masked man on her way home. The decisive factor was that Taiki's bodily fluids were found in Rie's vagina after she was rushed to the hospital, and his favorite fountain pen was found at the scene.