Chapters 3 through 12 of the light novel detail the harrowing escape and subsequent life of two siblings, Jin-ta and Suzune, and their integration into the secluded village of Kuzuno. Jin-ta, a young boy, flees Edo with his younger sister Suzune to escape their abusive father. Suzune, who is blind in her right eye and wears a bandage over it, is the primary motivation for Jin-ta's actions. He feels immense guilt for not being able to protect her from their father's abuse.
While stranded on a road in the rain, they are approached by a man named Genji, who offers them shelter. Despite initial suspicion, Jin-ta accepts, recognizing their desperate situation. Genji, a "Miko-mori" (shrine guardian), leads them to Kuzuno, a mountain village known for its ironworks and skilled swordsmiths. Upon arrival, they meet Genji's daughter, Shirayuki, a kind and welcoming girl who immediately accepts them. Suzune, witnessing Shirayuki's happy family life, feels a pang of sadness for what she has lost, but Jin-ta reassures her.
The narrative then jumps forward four years. Jin-ta, now training diligently in swordsmanship under Genji, aspires to become strong enough to protect Suzune and Shirayuki. Suzune has adapted to village life and befriended a girl named Chitose. Jin-ta's training is rigorous, and he often loses to Genji, but he is encouraged by Shirayuki's unwavering support. He learns that Genji's wife, Yokaze, is the "Itsuki-hime," a priestess who resides in a shrine on a hill and is considered the "elder" of Kuzuno.
The story then shifts to a more mature Jin-ta, now eighteen, who works as a "Kiri-yaku" (demon slayer) and a "Miko-mori" for the current Itsuki-hime, Byakuya, who is Shirayuki in her priestly role. He is tasked with protecting Kuzuno from demons that have begun to appear more frequently. During a mission, Jin-ta encounters and defeats a demon disguised as a woman. He learns that demons are targeting Kuzuno, possibly for the Itsuki-hime or the sacred sword "Yorai."
The chapters also delve into the complex relationships within Kuzuno. Jin-ta, despite his Miko-mori duties, struggles with his own sense of inadequacy, feeling he lacks the artisan skills valued in Kuzuno. He also navigates his complicated feelings for Shirayuki, who, as the Itsuki-hime Byakuya, has taken on a sacred role that separates her from her past. Their interactions reveal a deep, unspoken affection, but also the societal constraints that keep them apart.
A significant turning point occurs when it's revealed that Shirayuki, now Byakuya, is to be married to Kiyomasa, the village chief's son and Jin-ta's fellow Miko-mori. This arranged marriage is a political move to secure Kuzuno's future and lineage, despite Byakuya's feelings for Jin-ta. Jin-ta, understanding the importance of her role and his own inability to abandon his path, accepts this painful reality, acknowledging that their paths have diverged.
Meanwhile, Suzune, who has remained physically unchanged since their arrival in Kuzuno, harbors a deep, possessive love for Jin-ta. When she learns of Byakuya's impending marriage, her jealousy and resentment manifest in a terrifying transformation. Influenced by a demon who reveals Byakuya's perceived betrayal of Jin-ta, Suzune, who is revealed to have demonic blood, transforms into a powerful demoness herself and attacks Byakuya.
The climax of these chapters sees Jin-ta, after a brutal battle with a powerful demon, returning to find Byakuya murdered by Suzune. Overwhelmed by grief and rage, Jin-ta himself succumbs to his demonic heritage, transforming into a demon to exact revenge on his sister. The narrative ends with Jin-ta, now a demon, confronting Suzune, setting the stage for a tragic confrontation between the siblings.
