She is friends with Yoriko Kusumoto and sees Yoriko as her reincarnation. She was then pushed by Yoriko at the train station and severely injured. Later, she is revealed to be involved in an experiment where her head is put into a small box where she is somehow still alive for at least a few days after being taken away by Amemiya, who is in love with her. Youko, who at first claimed to be her sister, is actually her mother. She is the result of the incestuous relationship between Youko and her father, Koushirou Mimasaka.
