The Tatsumiya family members are central figures across the narrative. Yukari Tatsumiya, a young woman residing in early 20th century Tokyo, possesses innate psychic abilities. These powers draw the attention of antagonist Yasunori Kato, who kidnaps her. Kato intends to use Yukari as a medium to awaken the vengeful spirit of Taira no Masakado and destroy Tokyo. During her captivity, Kato employs dark magic to forcibly impregnate her, believing the resulting child will have greater spiritual potential for his plans. Rescued by allies of the onmyoji Yasumasa Hirai, Yukari returns home deeply traumatized. Her mental state deteriorates significantly, haunted by nightmares and psychological instability. Her brother, Yoichiro Tatsumiya, harbors complex and ultimately destructive feelings towards her, culminating in a non-consensual act of brother-sister incest.

Yukari gives birth to a daughter, Yukiko Tatsumiya. Yukiko inherits her mother's spiritual sensitivity. Years later, upon reaching adolescence, Yukiko becomes a target for Kato. He kidnaps her from the Tatsumiya home, intending to use her as a vessel for Masakado's spirit due to her bloodline connection and heightened powers. Yukari's persistent mental fragility largely prevents her from directly protecting her daughter.

Later, powerful shrine maiden Keiko Mekata enters the family. Spiritually guided by Masakado's spirit to oppose Kato, she encounters and marries Yoichiro Tatsumiya, taking the name Keiko Tatsumiya. As a household member, she assumes the role of spiritual protector for Yukari and Yukiko. Keiko directly confronts Kato multiple times, notably pursuing him underground after he kidnaps Yukiko again and engaging him in magical battles. During the final confrontation with Kato, Keiko draws upon spiritual aid and Masakado's power, ultimately channeling the boundless compassion of the bodhisattva Kannon (Kwannon). This act of divine compassion appeases the ancestral curse fueling Kato's hatred, leading to his dissolution and ending his threat.

Yukiko survives her ordeals, freed after the robot Gakutensoku's self-destruction disrupts Kato's plans involving the Underground Dragon. Keiko Tatsumiya's actions secure the family's safety from Kato's immediate threats, solidifying her role as the family's guardian. The legacy of the Tatsumiya women is intrinsically linked to the spiritual defense of Tokyo against Kato's machinations, spanning generations and defined by trauma, inherited power, resilience, and ultimately, the protective strength embodied by Keiko's final intervention.