Tsumiki Kashiwagi is a daydreaming high school student whose life is shattered when she encounters Isuka, a witch pursued by ruthless hunters. After both girls are subjected to a brutal assault by monstrous creatures, Tsumiki unexpectedly absorbs a powerful magic stone called a Maseki. Suddenly granted supernatural powers, Tsumiki is thrust into a violent conflict between humans, witches, and the Mazoku.
After revealing her identity as a witch to Tsumiki, Isuka discovers that Kashiwagi possesses a precious magical shard called a maseki. Their school day turns into a nightmare when their teacher reveals himself as the demon Genji, who traps them in a distorted realm to break Isuka and enslave Kashiwagi. Just as Genji seems victorious, the maseki within Kashiwagi triggers a powerful awakening, allowing Isuka to unleash a devastating attack and repel the demon.
After being defeated and captured, Isuka discovers that her sister Tia has been possessed by a malevolent entity. The monster subjects Isuka to a series of horrific physical mutations and forced pregnancies, breaking her will and transforming her body into a vessel for monster offspring. Ultimately, Isuka succumbs to the corruption, descending into a state of mindless lust alongside the corrupted Tia.