Born a women in Kyoto under the name Sukehime Ayako, the Lady of the Full Moon got her nickname from a poem that was given to her by the current Mikado. Shortly afterwards, she gave birth to his first child, and it was her hope that their son, Hirohira, would become prince of Kyoto. However, it was not to be. Several years later, the Mikado took a liking to the Minister of the Left's daughter, and had a son with her named Atsuhira. News of this made Ayako furious as she was still madly in love with the Mikado.

Ayako fell under a great depression and would often visit court noble Hiromasa to listen to his famous flute playing, making sure not to revel her identity. Still, her feelings would not go away, even as Hiromasa himself fell in love with Ayako and promised her the moon itself if it would lift her from her depression. It was at this point that Ayako reveals her identity to the court noble, telling him "if only they had met sooner..." as she rides off.

Meanwhile the Minister of the Right, Motokata, is displeased with the birth of the new prince. He fears that this would give the Minister of the Left more power over the court. So he forms an allegiance with Doson, the head onmyoji teacher at Kyoto, to deal with the prince. Doson curses the new born prince Atsuhira with a powerful spell, in which he hopes would kill the prince while at the same time making it look like a act of mere demons. The plan fails, though, when Seimei intervenes. Using Lady Aone, Seimei is able to remove the spell from the newborn prince. In retaliation, the Minister of the Right charges the two with placing the curse on Atsuhira. However, the Minister of the Right has no proof to charge the two with, so in a fit of rage he orders the soldiers to cut them down. The Minister of the Left interrupts the trial, telling Motokata he's out of place making such an order without the approval of the Mikado, and orders the two free.

After this string of setbacks, Motokata tries to back out of his allegiance with the head Onmyoji teacher, but Doson informs him that he is too late, as the next blow against the prince is already in motion. This next attack reveals itself to be the Lady of the Full Moon herself. First, Ayako visits the daughter of the Minister of the Left while she is putting her son to sleep. Ayako curses the room, causing straw figures with nails driven through them and a decapitated head to fall from the ceiling. All the while she chants, insisting that the prince be given to her, and then vanishes.

The Minister of the Left goes to Seimei and pleas with him to, once again, help the prince. Seimei explains that this sounds to be the work of Namanari, a half demon, half human creature. Eventually Seimei agrees to help and enlists the aid of Hiromasa. Seimei sets up a holy precinct in the Mikado's room, where he places a large straw figure and a small straw figure in the center of the room. Seimei warns Hiromasa and the Mikado that while the creature is present neither is to utter a word as that would break the spell and endanger them both.

That night, the Lady of the Full Moon, driven onwards by Doson's chants, once again pays visit to the prince. Once she enters the Mikado's room Seimei's spell takes affect, making him invisible to the creature, and, at the same time, creating the illusion that the stray figures in the room are the Mikado and the young prince. Ayako expresses her feelings for the Mikado to the illusion until she lays eyes on the small straw figure in the room, at which point she strangles it and tosses it away. Still consumed by rage, Ayako takes a nail and drives it into the large stray figure's head, and then weeps. She then starts reciting the poem of the full moon that the Mikado had given to her. It's at this point that the Mikado speaks, interrupting her by finishing the poem and at last realizing that this creature is in fact Ayako. Only after speaking does the Mikado realize the mistake he has made, as the spell is broken. Ayako charges at the voice she heard, hammer in hand, before Hiromasa moves into her path. Ayako stops in her tracks, but only to laugh at Hiromasa before she charges him instead with the hammer. Seimei sneaks up behind her and removes a scripture from her back, dispelling Doson's influence.

With Doson's influence removed, Ayako becomes aware of what she is doing and starts to weep upon the sight of Hiromasa. However, Doson's power over Ayako has not come to an end, as he mutters another spell, this time forcing Ayako into a demon-like form: the Namanari.

Once again under the influence of Doson, Namanari attacks the Mikado, tackling both Hiromasa and Seimei out of the way. The two quickly regain their composure, and, as Seimei rushes the Mikado off to safety, Hiromasa offers himself to the demon. The demon complies by biting into his arm. Under immense pain, Hiromasa explains that he doesn't mind, and to "strike deep Milady." At which point the creature stops and looks Hiromasa eye-to-eye. Doson's influence is temporarily broken, as the Namanari quickly unsheathes Hiromasa's sword and slits her own throat. Destroying her demon side, shortly before she herself dies.