"Caterpillar" is a psychological and supernatural manga that explores themes of identity, transformation, and the human condition. The narrative centers around a young man named Shou, who awakens in a mysterious, desolate world with no memory of his past. He discovers that his body has been transformed into a grotesque, insect-like form, resembling a caterpillar. This physical metamorphosis becomes a central metaphor for his internal struggle and the broader existential questions posed by the story.

As Shou navigates this strange world, he encounters other individuals who have undergone similar transformations, each representing different stages of their psychological and emotional evolution. These characters include a woman named Rin, who has become a butterfly-like being, symbolizing freedom and transcendence, and a man named Kuro, whose monstrous form reflects his inner turmoil and despair. The interactions between these characters reveal their shared experiences of loss, guilt, and the search for meaning in a world that seems devoid of purpose.

The plot unfolds through a series of episodic encounters, with Shou and the others confronting both external threats and their own inner demons. The world they inhabit is filled with surreal landscapes and bizarre creatures, creating an atmosphere of unease and uncertainty. As Shou pieces together fragments of his memories, he begins to uncover the truth about his transformation and the nature of the world around him. This journey of self-discovery is marked by moments of intense introspection and emotional revelation, as Shou grapples with questions of identity, morality, and the possibility of redemption.

The narrative structure of "Caterpillar" is non-linear, with frequent flashbacks and shifts in perspective that add depth to the characters and their motivations. The story delves into the psychological impact of their transformations, exploring how their altered states affect their sense of self and their relationships with others. The manga also incorporates elements of horror and suspense, with the characters facing both physical dangers and the haunting specters of their pasts.

Throughout the series, the theme of metamorphosis is explored in various forms, from the literal transformation of the characters' bodies to the metaphorical changes in their minds and spirits. The manga raises questions about the nature of humanity, the boundaries between self and other, and the possibility of transcendence through suffering and self-awareness. The ending of the series leaves many questions unanswered, emphasizing the ambiguity and complexity of the characters' journeys and the world they inhabit.