"Shojyo Koakuma Kei: The Writhing Women" is a psychological and supernatural anime series that explores themes of control, identity, and transformation. The narrative centers on a group of high school girls who become entangled in a mysterious and sinister phenomenon. The story begins when the protagonist, a reserved and introverted student named Aya, discovers a strange, pulsating mark on her body. This mark, which appears to have a life of its own, begins to spread and influence her thoughts and actions, leading her down a path of increasing paranoia and desperation.

As the mark spreads, Aya learns that she is not alone in her predicament. Other girls in her school, including the confident and popular Rina and the quiet, observant Yuki, also bear similar marks. These marks grant them unnatural abilities, such as heightened senses and physical strength, but at a cost: the marks demand obedience and feed on their hosts' emotions, particularly fear and anger. The girls soon realize that the marks are connected to an ancient entity that thrives on human suffering and seeks to manipulate them into fulfilling its dark agenda.

The series delves into the psychological toll of the marks on the girls as they struggle to maintain their sense of self. Aya, initially passive and withdrawn, becomes increasingly assertive as she fights to resist the entity's influence. Rina, who initially embraces the power the mark grants her, begins to question her own morality as she witnesses the destruction it causes. Yuki, who is more analytical, attempts to uncover the origins of the marks and the entity behind them, but her investigations lead her to uncover unsettling truths about her own past.

As the story progresses, the girls are forced to confront not only the external threat posed by the entity but also their own inner demons. The marks amplify their insecurities and fears, leading to conflicts both within the group and with those around them. The series builds tension as the girls' relationships fracture under the strain, and they must decide whether to succumb to the entity's control or find a way to break free.

The narrative is punctuated by moments of intense psychological horror and surreal imagery, as the entity's influence manifests in increasingly disturbing ways. The girls' struggle for autonomy and their fight against the encroaching darkness form the core of the story, culminating in a climactic confrontation that tests their resolve and forces them to make difficult choices about their futures.