Captured by a deputy shogun and his vassal in feudal Japan, Towa Higurashi is told the story of an event that took place over a decade ago, when Inuyasha, Kagome, and their friends were attacked by a demon called Root Head.
10 years ago, in the feudal era, Towa and Setsuna were sisters living in a forest until a fire broke out. During the fire, the two became separated and Towa was drawn into a time portal that sent her into the future to modern day Japan.
Setsuna and Moroha arrive with a demon in the modern era through the Sacred Tree at Higurashi Shrine. Towa is reunited with Setsuna, but Setsuna has no memories of her and refuses to believe that Towa is her twin sister.
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.
Back in the feudal era, Towa and Setsuna take on a job to slay a demon Jakotsumaru, a demon boy who is stealing the bones of humans and animals. They meet up with Moroha, who arrives to claim a bounty for Jakotsumaru's father, Tokotsu.
Travelers are going missing one after another. Towa, Setsuna, and Moroha head to the northern mountains to crack the case, but instead they find a village completely overrun by ghost cats.
Towa goes to search for the Dream Butterfly. When she gets lost, she encounters a pirate named Riku, who is trying to find his ship. When Towa helps him out, Riku presents her with the real Kikujumonji sword.
Towa, Setsuna, and Moroha chase after Yotsume, who flees to Kyuki's lair. With the help of a Rainbow Pearl from Kyuki, Yotsume casts a spell on the girls to put them to sleep and discover their weaknesses through their dreams.
The Half-Demon Princesses are tasked with slaying Kinka and Ginka, conjoined twins of the Ka Demon Tribe whose battles for dominance have been wreaking havoc everywhere.
Towa and Setsuna learn about a pond that devours any human or animal that comes near it. When they go investigate it, they come across two siblings who lost their parents to the pond.
Konton sends the demon Nikosen, a former human sage, to kill Towa, Setsuna, and Moroha. Being lured to him by his poison, the girls battle Nikosen. But as the nighttime approaches, Towa suddenly finds her demonic powers are fading away.
The demon Totetsu, one of the Four Perils, is hunting down and devouring monks found throughout the land. Kohaku sends Hisui, Towa, and Setsuna, to find Hisui's father, Miroku, to guard and protect him from the man-eating demon.
Towa, Setsuna and Moroha go to slay a mountain god, Homura, who had abducted a beautiful girl. When the girls find him, Homura is shocked by Towa and Setsuna's presence, believing to have killed the twins in the forest fire years ago.
The truth behind the night that sealed the fate of Towa, Setsuna, and Moroha's parents is finally revealed. It began four years before Towa and Setsuna were born, the day Hosenki II gave Inuyasha the Black Pearl.
Konton barters with Yawaragi, Moroha's former master, to take Moroha's life in exchange for an item she seeks. Yawaragi appears before Moroha, and a showdown between master and pupil begins.
Riku informs Towa, Setsuna, and Moroha about the whereabouts of Totetsu and they set out to slay him. In their pursuit, Totetsu leads them to a ravine where, unbeknownst to the girls, Konton has set up a trap to ensnare and destroy them.
Towa and Setsuna break free from Konton's trap and defeat him. They meet up with Moroha to finish off Totetsu, but he flees the battle. The girls chase after him but are suddenly attacked and find themselves face to face with Kirinmaru.
The demon slayers are offered a chance to be employed by the deputy shogun, but they must battle against a group of bounty hunters, which includes Moroha. Not wanting Towa to get involved, the two parties try to keep the battle a secret.
On the night of the new moon, Towa is visited by Riku and he reveals his intentions of gathering all seven of the Rainbows Pearls. During their conversation, Totetsu suddenly appears to attack the currently powerless Towa.
Zero appears before the girls and removes the seal suppressing Setsuna's demon powers. When Setsuna transforms and loses control, Towa and Moroha struggle to stop her rampage.
Towa and Setsuna hire Moroha to assist them with slaying Zero. They go to the location where the Great Dog Demon had perished long ago and find Zero, but Riku is there to defend her.
Zero cuts ties with her younger brother and flees the scene. Towa, Setsuna, and Moroha are left to confront Kirinmaru, but in the face of overwhelming power, they must pay a great price.
