Half-demon twins Towa and Setsuna are separated from each other when a mysterious tunnel sends Towa into the future, where she is found and raised by Kagome Higurashi’s brother Sota.

Towa decides to return to the feudal era to help Setsuna regain her memories. The trio enter the corridor leading to the feudal era, but within it awaits the spirit of a certain priestess.

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

Setsuna and Towa hire Moroha to help slay Zero. The trio successfully track Zero down, but Riku stands in their way.

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.

Osamu Kirin has been quietly exterminating the demons that have been appearing in the present day. He asks Towa, Setsuna, and Moroha to slay demons at the concert that is happening.

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.

Osamu Kirin brings the Grim Comet to the feudal era. He convinces Rion that they are both hoping for the same world and promises to make it a reality. Meanwhile, Towa, Setsuna, and Moroha are stuck in the present day.

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.