Sedusa emerges as a villainous alter ego of Sakurako Kintoki (Annie in English), a local shopkeeper acquainted with the protagonists. Her transformation occurs after black Chemical Z-rays strike her during lipstick application, activating a curse that shifts her into Sedusa whenever she wears lipstick. This curse bestows the power to craft lifelike disguises with cosmetics and wield her hair as prehensile tentacles for combat. Both Sakurako and her Sedusa form harbor romantic feelings for Souichirou (Jason), an ordinary civilian unconnected to the Professor.

As Sakurako, she behaves shyly and kindly around Souichirou. The Sedusa persona, however, adopts an assertive and seductive demeanor, aggressively pursuing him with her charms. Episode 8 chronicles her initial transformation and subsequent attempts to enchant Souichirou, exploiting her abilities to gain his affection while villainous. These curse-driven shifts continually threaten her everyday existence.

A pivotal moment unfolds in episode 45 when Souichirou uncovers Sakurako’s dual identity. He confronts her, accepts her true self, and urges her to return to normal. Overwhelmed by emotion, she faints and awakens with total amnesia regarding Sedusa and her dual life, concluding her arc as an antagonist.