Towa Higurashi learns about an incident that took place decades ago involving a half demon named Inuyasha and a priestess named Kagome.
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.
A demon emerges in the present day with Setsuna, Towa's twin, and the bounty hunter Moroha in tow. Seeing Setsuna in trouble awakens Towa's latent demon powers.
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.
Towa and Setsuna take on a request to slay Jakotsumaru, a boy who has been extracting bones from humans and beasts in order to revive his father, the demon beast Tokotsu.