"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 the body of a powerful android. This android, named Nuku Nuku, is designed to protect Ryunosuke from his estranged mother, Akiko Natsume, who is the CEO of Mishima Heavy Industries. Akiko, determined to reclaim Nuku Nuku for her company's military applications, frequently sends advanced weaponry and agents to capture the android. However, Nuku Nuku's primary directive is to act as a loving and protective mother figure to Ryunosuke, often leading to chaotic and comedic situations as she balances her maternal instincts with her combat capabilities.

The series blends elements of science fiction, action, and comedy, with Nuku Nuku's dual nature as both a nurturing caretaker and a formidable warrior driving much of the plot. Her interactions with Ryunosuke and his classmates, as well as her battles against Akiko's forces, form the core of the narrative. Despite her advanced technology and combat skills, Nuku Nuku often displays childlike curiosity and naivety, which contrasts with her ability to effortlessly dismantle enemy robots and vehicles. This juxtaposition creates a lighthearted tone, even during intense action sequences.

Ryunosuke, while initially embarrassed by Nuku Nuku's over-the-top antics, gradually comes to appreciate her unwavering loyalty and affection. Akiko, on the other hand, remains a persistent antagonist, driven by her ambition and frustration at being outsmarted by her ex-husband's creation. The series explores themes of family, identity, and the ethical implications of artificial intelligence, though these are often presented in a humorous and exaggerated manner. The episodic structure allows for a mix of standalone adventures and overarching plotlines, with Nuku Nuku's unique abilities and personality serving as the focal point of each episode.