Saiko-chan, also known as Saiko and Sayaka Himura, is a high school student with an obsessive relationship with Akira. She comes from a wealthy family but experienced trauma as a child, witnessing her father commit murder. This, combined with neglect from her stepmother, led to psychological instability and Dissociative Identity Disorder. Saiko has a complex relationship with Akira, oscillating between intense love and terrifying rage. Her obsession drives her actions, and she is capable of both great kindness and extreme violence. She also has conflicts with Akira's friend, Shinji, who bullies her. Saiko's appearance varies depending on her mental state, ranging from a seemingly normal student to a terrifying, blood-soaked figure. Her personality shifts between a kind, loving girl and a violent, psychotic killer.