"Ningen Karimenchū" is a manga series that blends elements of comedy, slice-of-life, and surrealism. The story centers around a young man named Tetsuo, who discovers one day that his body has become infested with tiny humanoid creatures called "Karimenchū." These creatures, resembling miniature humans, live inside his body and emerge to interact with the world around them. Each Karimenchū has its own distinct personality, often reflecting exaggerated or absurd traits, and they frequently cause chaotic and humorous situations in Tetsuo's daily life.

Tetsuo's interactions with the Karimenchū form the core of the narrative. The creatures are not malicious but are highly unpredictable, often leading to bizarre and comedic scenarios. For instance, they might suddenly emerge to engage in activities like cooking, cleaning, or even holding meetings inside Tetsuo's body. Their presence creates a constant source of tension and humor as Tetsuo struggles to maintain a semblance of normalcy while dealing with their antics.

The series explores Tetsuo's relationships with those around him, including his family, friends, and coworkers, who are often drawn into the chaos caused by the Karimenchū. Some characters become aware of the creatures, while others remain oblivious, adding layers of situational comedy and misunderstanding. The manga also delves into the origins and nature of the Karimenchū, though this aspect is often treated with a lighthearted and surreal tone rather than a serious exploration.

Themes of absurdity, the mundane, and the surreal are woven throughout the story. The Karimenchū serve as a metaphor for the quirks and idiosyncrasies of human behavior, amplifying everyday situations into exaggerated and often ridiculous events. Despite the fantastical premise, the series maintains a grounded focus on Tetsuo's attempts to navigate his unusual circumstances, blending humor with moments of introspection about identity and human connection.

The artwork complements the tone of the story, with expressive character designs and dynamic paneling that enhance the comedic and surreal elements. The Karimenchū are depicted with exaggerated features and behaviors, emphasizing their role as both a source of chaos and a reflection of Tetsuo's inner world. The series balances its absurd humor with a sense of warmth, creating a unique and engaging narrative that appeals to fans of unconventional storytelling.