Towa Higurashi learns about an incident that took place decades ago involving a half demon named Inuyasha and a priestess named Kagome.

When a demon begins to devour virtuous monks and Shinto priests in the region, Hisui is assigned to guard his father, Miroku, who has been undergoing harsh training for the past two years.

Setsuna opens up to Towa about the hidden village for half-demons where she was raised for most of her childhood.

Zero removes the seal that Miroku placed on Setsuna to suppress her demon powers, awakening the latent demon blood within.

Moroha learns about her parents’ battle against Shogen Mamiana, the sealing of the Full Moon Raccoon Dog, and Takechiyo’s exile from his clan. Setsuna is attacked by the snow demon Yukinyudo. Zero targets Towa on the new moon.

In the present day, Osamu Kirin sees the Grim Comet approaching. Meanwhile, in the feudal era, Towa’s life is in danger after she uses her Zanseiken. The Spirit of the Tree of Ages orders the half-demon princesses to go destroy the Grim Comet.

Inuyasha and the others have their hands full with the evil spirits pouring out of the burning Windmill of Time. The three girls and Osamu Kirin try to stop the Grim Comet from falling to the earth.

Towa, Setsuna, and Moroha must save Rion, who has linked her fate with the Grim Butterfly, but Osamu Kirin stands in their way. Kirin declares that he and Rion should reign over the world in order to bring about true peace.

Setsuna directs Towa and Moroha as they continue to sever Rion’s threads of fate. Each time a thread is severed, more of Rion’s true feelings are revealed. As Kirinmaru fights Sesshomaru, he realizes the real reason he lost Rion.

The feudal era is saved from the Degenerate Age. Inuyasha helps repay Moroha’s remaining debt. Towa and Setsuna receive kimonos from their mother, Rin. Towa, Setsuna, and Moroha accept a demon-slaying request from a mysterious man.