"Nekojiru Udon" is a surreal and darkly comedic manga series that blends whimsical absurdity with unsettling undertones. The narrative centers on Nekojiru, a cat-like girl, and her younger brother, Nyatta, as they navigate a bizarre and often chaotic world filled with strange creatures, supernatural occurrences, and morally ambiguous situations. The story unfolds in a series of loosely connected vignettes, each presenting self-contained scenarios that range from humorous to disturbing.

Nekojiru and Nyatta frequently encounter eccentric characters, including anthropomorphic animals, ghosts, and deities, who often involve them in peculiar or dangerous situations. The siblings' interactions with these characters highlight themes of innocence, cruelty, and the unpredictability of life. Nekojiru, despite her childlike appearance, often displays a callous or indifferent attitude, while Nyatta, though naive, occasionally shows moments of unexpected resourcefulness. Their dynamic oscillates between sibling camaraderie and antagonism, adding depth to their relationship.

The plotlines are episodic, with each chapter presenting a new scenario. These scenarios often involve surreal transformations, dark humor, and abrupt shifts in tone. For example, one chapter might depict the siblings engaging in a whimsical adventure, while another might delve into unsettling or tragic events, such as encounters with death or existential dilemmas. The series frequently juxtaposes its whimsical art style with grim or violent content, creating a distinctive and jarring atmosphere.

Recurring motifs include the fragility of life, the inevitability of suffering, and the absurdity of existence. The manga does not shy away from exploring darker themes, such as loss, betrayal, and the consequences of selfishness, often presenting them in a matter-of-fact manner. Despite its often bleak tone, the series maintains a sense of dark humor, using absurdity and irony to underscore its themes.

The world of "Nekojiru Udon" is one where logic and morality are fluid, and the boundaries between reality and fantasy are blurred. This ambiguity allows the narrative to explore a wide range of ideas and emotions, often leaving readers to interpret the meaning behind the events. The series' unique blend of whimsy and darkness has made it a distinctive work within the manga medium, appealing to those who appreciate unconventional storytelling and complex thematic explorations.