Sayaka Ogata is the daughter of the swordsmith Amon Ogata. Amon discovered the infant Gai and adopted him, leading Sayaka to share a home with both her father and Gai, establishing their familial bond. She is present when Gai suffers a catastrophic accident during a ritual involving the demonic sword Shiryū, an event that costs him his right arm. Amon subsequently fuses the sentient Shiryū into Gai's body as a prosthetic limb, irrevocably binding Gai to the weapon's power. Later, Sayaka confronts her father, questioning Gai's motivations and actions as he struggles with the consequences of hosting the sentient sword. Her interactions reveal a profound concern for Gai's transformation and the inherent dangers stemming from his connection to Shiryū.