Pai Ayanokoji, last of the mystical Sanjiyan Unkara race identified by a third eye, originates from Tibet. Discovered by archaeologist Yakumo Fujii's father while researching her species, she manifests dual personalities due to her race's extreme longevity. Her primary persona, Pai, presents as a cheerful, naive girl, while the secondary Parvati IV emerges under threat or emotional distress, marked by her third eye opening. Parvati is stoic and wields potent magic, though using it exhausts her, demanding rest and leaving her vulnerable. Both personalities coexist and communicate internally.

Pai seeks humanity via the Ningen no Zō artifact, believing it transfers Sanjiyan powers to grant mortality, a process she blames for her race's decline. Meeting Yakumo Fujii, her benefactor's son, in Tokyo begins her journey. After Yakumo dies shielding her from her pet demon Takuhi, Pai absorbs his soul, transforming him into her immortal Wu servant. Yakumo's humanity hinges on Pai achieving mortality, irrevocably linking their fates.

Years later, in the "Legend of the Divine Demon" OVA, Pai resurfaces with amnesia, believing herself an ordinary schoolgirl. Yakumo, now a trained Wu, finds her and tries to restore her memories. Her Sanjiyan persona reemerges, equally amnesiac and confused, acting out from loneliness and identity loss. The twist reveals Pai's body was secretly possessed four years prior by the demon snake Houa Sho, sent by antagonist Benares to suppress her memories and control her for Kaiyanwang's resurrection ritual. Unintentionally amnesiac herself, Houa Sho genuinely believed she was Pai. Facing Benares's return, Houa Sho sacrifices herself to release Parvati, who destroys Benares and rewards Houa Sho by reincarnating her as a human with no memory.

Pai's character evolves throughout the broader narrative. Her bond with Yakumo deepens into mutual affection, complicating her quest. She confronts Kaiyanwang, the "mad Sanjiyan" responsible for her species' near-extinction centuries earlier. In the final arc, Parvati attempts self-sacrifice during a ritual to transfer her and clone Kali's powers to Kaiyanwang, hoping this fulfills Pai's wish for humanity alongside Yakumo. The ritual backfires: Kaiyanwang gains near-omnipotence, while Pai and Yakumo are forcibly turned mortal. As a vulnerable human, Pai protects the mortally wounded Yakumo during the apocalyptic conflict. Her bond with Parvati proves pivotal when they reunite within Kaiyanwang's consciousness, overpowering him and regaining their powers. This reunification revives Yakumo as her Wu. Ultimately, Yakumo sacrifices his physical form to resurrect humanity, with Pai/Parvati embarking on a quest to find him, assured of reunion by their restored immortal bond.

Pai's abilities include absorbing human souls to create near-invulnerable, regenerative Wu servants. Her magical powers, accessible only as Parvati, involve high-level spells drawing on finite energy, demanding recuperation after use. Her Sanjiyan physiology features non-human cellular structures and a brain detectable by advanced scans, though she appears human with her third eye closed. This dual personality reflects a species trait where younger Sanjiyans fragment under emotional stress, while older ones grow callous.