"Kesou no Yamai" is a psychological thriller manga that delves into themes of identity, obsession, and the fragility of human perception. The narrative centers around a young woman named Aya, who becomes entangled in a disturbing series of events after encountering a mysterious man named Kiri. Kiri claims to have the ability to "cure" people of their emotional and psychological ailments by altering their appearances, effectively erasing their past identities. His methods, however, are deeply unsettling, involving extreme physical transformations that leave his subjects unrecognizable, both to themselves and to others.

Aya, initially skeptical, is drawn into Kiri's world after witnessing the drastic changes in those he has "treated." As she becomes more involved, she begins to question her own sense of self and reality. The story explores the psychological toll of Kiri's interventions, as his subjects struggle with the loss of their former identities and the societal rejection they face. Aya's own mental state deteriorates as she grapples with the ethical implications of Kiri's actions and her growing dependence on his approval.

The manga is structured around a series of episodic encounters with Kiri's clients, each of whom presents a unique case that highlights different facets of identity and self-perception. These vignettes serve to deepen the central conflict, as Aya becomes increasingly conflicted about her role in Kiri's experiments. The narrative builds tension through its exploration of the blurred line between liberation and destruction, as Kiri's methods challenge conventional notions of self-improvement and mental health.

Kiri himself is portrayed as an enigmatic and morally ambiguous figure, whose motivations remain unclear throughout much of the story. His calm demeanor and persuasive rhetoric mask a deeply manipulative nature, making him both a compelling and unsettling character. Aya, in contrast, serves as the audience's anchor, her gradual unraveling mirroring the reader's own unease as the story progresses.

The manga's pacing is deliberate, with a focus on psychological tension rather than action. The artwork complements the narrative, using stark contrasts and unsettling imagery to emphasize the themes of transformation and disorientation. The story culminates in a climactic confrontation that forces Aya to confront the consequences of her choices and the true nature of Kiri's intentions. The ending leaves significant questions unresolved, reflecting the manga's overarching exploration of identity and the human psyche.