Saku Kajiwara holds the position of Priestess of the Black Dragon (Kokuryū no Miko). This role grants her spiritual authority distinct from Nozomi Kasuga's status as the White Dragon Priestess. At 18 years old, she is roughly one year older than Nozomi, yet affectionately calls her "twin," reflecting their close sisterly bond. Saku is the younger sister of Kagetoki Kajiwara, one of the Eight Guardians sworn to protect the White Dragon Priestess. This familial tie aligns her with the Genji forces, though her primary narrative importance derives from her role as the Black Dragon Priestess.

Saku shares a romantic bond with the Black Dragon God (Kokuryū), a key element of her history. This relationship suffered when Kokuryū vanished mysteriously, leaving her without her divine counterpart. His absence profoundly affected her, though the specific reasons for his disappearance remain unknown. Despite this personal loss, Saku exhibits resilience and maturity. She channels her expertise into aiding others, notably teaching Nozomi her proficiency in traditional Japanese dance. Recognizing Nozomi's need for guidance in their new world, Saku provides her with a fan and instructs her, an act demonstrating her supportive nature and cultural knowledge.

Her story continues into the sequel "Unmei no Labyrinth," where she appears among the returning cast. While other main characters receive dedicated romantic conclusions, Saku does not have a specific ending route focused on her. She remains connected to the core group and participates in the events surrounding the dimensional labyrinth threatening their world. Her presence contributes to the ongoing efforts to restore balance.