Sanae's background revealed that she had committed various crimes since she was in the nursing school, where she also was a skilled judo fighter. Despite her unattractive appearance at time, the villainess had succeeded in conning many rich men into marrying her, coerced them into her insurance scheme, and murdered them to claim huge amount of money. Unfortunately for Sanae, one of her targets, the secluded dentist Minoru Suzuki, escaped from her attack after came to know her true agenda, and the police had begun to caught the trail of her criminal action. During this time, Takao had located her and explained that he knew her entire background. As she was contemplating in silencing him, Takato proposed the villainess joining his criminal group, the Olypius Twelves, as Artemic of chastity, which he will also provide help inform of criminal art and fund, but also added that Sanae must first undergo a "makeover". Interested in Takato's proposal, the evil Sanae accepted his deal and underwent plastic surgery to become attractive and lost a huge amount of weight to fit Takako's goal. Following Takato's arrest and sentecing to death by his antithesis and detective Hajime Kindaichi, Inspector Isamu Kenmochi, and Superintendent Kengo Akechi, the evil Sanae continued to operate under her own agenda, and had not been caught by the police for many years until she eventually met her downfall at the hand of Hajime.
In the present day, the evil Sanae joined the trip to Uta Island that belonged to Otowa Black PR Company with Hajime and his subordinate Marin Hayama as the tour guides in a scheme to seduce a rich bachelor.
After being informed of Sanae's arrest and interrogation, Takato send a coded instruction to his subordinate outside the prison through "The Count of Monte Cristo" to eliminate Sanae due to her failure and arrest. The subordinate then sent a clothing and poisoned disposable contact lens to the unsuspecting Sanae, who was killed the moment she put it on.