Sayoko Toyama enlists private investigator Goro Nanase to find her missing husband, Tsuyoshi Toyama. She suspects Tsuyoshi is the murder suspect featured in recent news reports, initiating the search for his whereabouts and actions.

As Tsuyoshi's wife and mother to their son Keita, Sayoko endured a traumatic family car accident three years earlier. In that incident, Tsuyoshi faced an impossible choice, resulting in their daughter's death while saving Keita. This tragedy profoundly fractured the family's stability.

With the accident's third anniversary looming, Tsuyoshi's mental state deteriorates drastically. Sayoko becomes aware of his escalating instability and his dangerous plan to "reunite" their family. Her motivations are driven by the fierce determination to prevent further tragedy and shield both her husband and surviving son from harm. She actively participates in efforts to locate Tsuyoshi and intervene before his plans claim more victims.

The unresolved grief and trauma from their daughter's loss, combined with Tsuyoshi's psychological collapse, define Sayoko's narrative role. Her actions reflect a desperate struggle to hold her remaining family together amidst the escalating crisis.