"All Purpose Cultural Cat Girl Nuku Nuku" centers around Ryunosuke Natsume, a young boy whose life takes a dramatic turn when his father, Kyusaku Natsume, a brilliant but eccentric scientist, installs the brain of a stray cat into a highly advanced android body. This android, named Nuku Nuku, is designed to protect Ryunosuke and serve as a surrogate mother figure after his parents' separation. Nuku Nuku's feline instincts and superhuman abilities often lead to chaotic and comedic situations, blending action with lighthearted humor.

The series explores the dynamic between Ryunosuke, Nuku Nuku, and Kyusaku, as well as Ryunosuke's mother, Akiko Natsume, who is the CEO of a powerful corporation. Akiko views Nuku Nuku as a threat and frequently sends agents to capture or destroy her, creating a recurring conflict. Despite her corporate ruthlessness, Akiko's actions are driven by a desire to reconnect with her son, adding emotional depth to the narrative.

Nuku Nuku herself is a central figure, embodying both the innocence of a cat and the strength of a combat-ready android. Her interactions with Ryunosuke highlight themes of family, loyalty, and the blending of human and artificial life. The series balances episodic adventures with an overarching plot, often featuring Nuku Nuku thwarting Akiko's schemes while navigating everyday challenges with Ryunosuke.

The tone of the series is predominantly comedic, with slapstick humor and exaggerated action sequences, but it also touches on more serious themes, such as the complexities of familial relationships and the ethical implications of advanced technology. The characters are distinct and well-defined, with Nuku Nuku's dual nature as a cat and android providing a unique perspective on human behavior and emotions. The interplay between the main cast drives the story forward, creating a mix of heartfelt moments and over-the-top antics that define the series.