Sachiko Juraku is the primary antagonist and Public Morals Committee Chairwoman at Hyakkaou Private Academy. She possesses knee-length silver or light gray hair, with one strand reaching her waist, narrow red eyes featuring cat-like pupils, and often wears black or dark blue nail polish. Her academy uniform includes a black tie and high-heeled ankle boots instead of loafers. She visibly keeps a personal housepet, Mikura Sado, on a leash. Her personality exhibits extreme sadism devoid of empathy. She derives pleasure from inflicting physical and mental suffering to dismantle identities, motivating Mikura's enslavement. She particularly relishes breaking resilient individuals like Mary Saotome. While valuing obedience, she prioritizes humiliating those who resist her dominance. Her demeanor presents a cold, cruel interior beneath an elegant facade of calculated composure. She ascended within the Student Council through exceptional gambling prowess: heightened perception of opponents' movements, ingenuity, and capacity to detect cheats. She secured victories to crush opponents' wills, gaining popularity until challenges ceased. Her history with Mikura began with a gambling victory, followed by systematic degradation – enforcing a dog collar, public leashing, and physical humiliation. After repeated rematches and further defeats, Mikura submitted upon realizing a masochistic desire for domination. Within narrative events, she instigates confrontations to dismantle gambling dens, leading to her encounter with Mary Saotome. Intrigued by Mary's defiance, she engineers high-stakes gambles. One gamble involved Mary risking becoming her second housepet, a fate Mary narrowly escaped. Sachiko's fixation intensified; she orchestrated subsequent gambles like the Coupling Party and a treasure hunt where she deliberately selected a dog collar anticipating Mary's victory. Her manipulation included gaslighting Mary about Tsuzura's betrayal and employing sexual harassment as intimidation. Her campaign culminated in a forced Doubt Poker match. Demonstrating her gambling methodology, she gained dominance by interpreting Mary's micro-reactions and patterns after observing her across multiple games, without cheating. This psychological dismantling led to Mary's comprehensive defeat and debt, resulting in an ultimatum of enslavement or joining the Zenshoukai group. Mary circumvented this through external means, deepening Sachiko's obsession. Concurrently, she feigned concern over Aoi Mibuomi's schemes against Kirari Momobami while privately relishing the potential conflict. Her capabilities center on acute observational skills and psychological insight. She excels at reading opponents' involuntary physical tells and strategic patterns during gambles, rendering cheating unnecessary for her victories. This skill set establishes her as a formidable gambler reliant on perception and prediction.