Saizo is a young girl raised to present as male, a consequence of her background in theatrical traditions that prohibited female performers. Her father, a homosexual man, enforced masculine behaviors and appearance while rigorously training her in performance arts from early childhood. This training included instruction in a specific ritual dance capable of attracting supernatural entities called Yōi, derived from the mythological dance that lured the goddess Amaterasu from her cave.

Tragedy struck her formative years when her father perished in a fire after she accidentally interrupted an intimate moment between him and his male lover. She internalized deep-seated guilt, interpreting her given name—phonetically associated with the Japanese word for "sin" or "blame"—as proof of an inherent wickedness that caused his death. This belief fuels persistent self-loathing beneath her outward competence.

Functioning within the demon-hunting group Ayashi, Saizo employs a specialized paper fan that unfolds into an elongated, rope-like weapon for restraining Yōi creatures. Her role leverages both combat utility and her inherited dance, which serves tactical purposes against supernatural threats. Her personality reflects guardedness and emotional restraint, likely compounded by unresolved trauma and enforced identity suppression. She is approximately fourteen years old during the story's events; her thirteenth year coincided with her father's behavioral shift preceding the fatal fire.

Saizo's established background centers on internal conflict stemming from paternal loss, culturally mandated gender deception, and the burden of a name symbolizing self-perceived corruption. Her skills remain vital to the Ayashi's operations against otherworldly incursions.