Princess Mayu belongs to the Nakura Clan nobility in the Tokugawa era. Her kidnapping by the Seki Ninja triggers the central plot. The ninja created a diversion with a rampaging white tiger to abduct her, holding her hostage to demand the Ginryu Sword as ransom and threatening her murder if refused.

During captivity, the Seki Ninja subjected her to psychological and physical exploitation. They forced her into an opium-induced state and manipulated her participation in a lesbian orgy conducted by their female operatives. This formed an additional scheme to coerce her into surrendering the Ginryu Sword independently, despite her existing hostage status. When rescued, she directly questioned her rescuer about the nature of love, revealing emotional vulnerability amidst her trauma.

After returning to the Nakura Clan, clan leader Daizen Imura betrayed her rescuer, ordering execution for contact with her. Mayu intervened decisively, physically placing herself before the firing squad to stop the execution. She immediately collapsed afterward, exhibiting poisoning symptoms—coughing up blood—administered by the Seki Ninja during captivity. The poisoning's source and consequences remain unresolved.

Her interactions with the protagonist show unreciprocated emotional attachment. She openly declared her belief in his inherent goodness despite his violent profession, contrasting sharply with her horrified reaction to his confession of patricide and fratricide. Her fate following her return to the clan and succumbing to the poison is not elaborated upon.