Sachi (幸) is a 14-year-old middle school student. At the beginning of the story, her real name is unknown as she is only referred to as "XXX", sometimes with the honorific "-san". "Onii-san", her kidnapper, gives her the name "Sachi" to replace the name she had during her old life.
Sachi is a 14-year-old victim of her abusive parents and was bullied by her friends at school. Sick of her own life, she decides to end her own life before the "older brother" saved her life.