Sachiko Shinozaki is a former student of Heavenly Host Elementary School, and one of the recorded victims of the 1973 serial kidnappings and murders at the school. Her ghost rules the multidimensional nexus where Heavenly Host exists, making her the main antagonist of the Corpse Party series.
Sachiko was a student of Heavenly Host Elementary School in 1953. She witnessed the death of her mother Yoshie, a nurse at the school, after the school principal chased Yoshie into a stairwell where she slipped and fell to silence her over his attempts to rape her. Sachiko was subsequently murdered by the principal to keep her quiet as well, and her body was hidden in the basement of the school. Yoshie, Sachiko's mother, is the school nurse of Heavenly Host Elementary. Principal Yanagihori had an attraction towards her and one day made his attempt to rape her, advent. Yoshie ran to get away from him, only to slip down the staircase and snap her neck. Sachiko was at the bottom of the stairwell, where she witnessed the life of her mother fading from her body. She made an attempt to run however, the strides of a 7-year old were only so far. She was caught and strangulated by the principal as a means to cover up Yoshie's murder. Sachiko's corpse was buried in the basement of the school. While dying under such conditions gave birth to a deep grudge, cursing Yanagihori; appearing in his dreams causing his mind to become delusional and believes that she is still able to contact others in their dreams. Afraid that she would attempt to tell others about the incident, he digs her corpse up from the basement and removes her tongue with a pair of sewing scissors, after doing so, he then begins stabbing her corpse with the shears. Saying that he would continue to kill her as many times as it would take to remove her from his dreams. Her curse reached out and took hold of the principal's son, Yoshikaze. Yoshikaze slowly began to lose his mentality and will, eventually, his speech became incoherent, reduced to nothing more but grunts and moans. Finally, losing his humanity entirely, he ultimately becomes Sachiko's puppet.
