Sayoko is a priestess who imparts crucial knowledge to Kouichi about the ongoing conflict between deities, detailing the god Susanoo's role in battling the dragon spirits possessing Terumi. She serves as an exposition source for the mythological foundations of this struggle, clarifying the stakes and the ancient forces at play. Her interactions focus on conveying the harsh reality that Kouichi must accept Susanoo's possession to confront the dragons, while revealing the lethal cost of this alliance: Susanoo's victory requires the death of his human host. This knowledge forces Kouichi into a dilemma between his duty to defeat the dragons and his desire to save Terumi.