OVA
Description
Atsuko Natsume, universally known as Nuku Nuku, began as a critically injured cat rescued by Ryunosuke Natsume during his father Kyusaku Natsume's escape from Mishima Heavy Industries. To save the dying cat and console Ryunosuke, Kyusaku transplanted its brain into a stolen prototype android body, NK-1124, originally developed by Mishima. This created a unique being with a cat's consciousness inhabiting a humanoid robotic form resembling a teenage girl, integrated into the Natsume family as Ryunosuke's sister and protector.

Her android body grants exceptional physical capabilities: superhuman strength enabling her to lift multiple tons, immense durability allowing her to withstand bullets, explosives, and high-impact falls without damage, and superspeed permitting rapid movement including vertical surfaces. She possesses enhanced feline senses, particularly hearing and smell, and deploys retractable antennae from her head resembling cat ears, believed to enhance sensory data processing. Key vulnerabilities include extreme density preventing swimming without specialized equipment like the Mermaid Machine RX73, and susceptibility to disorientation from catnip. She exhibits biological traits such as eating, sleeping, and requiring oxygen, though the necessity beyond sustaining organic components remains ambiguous.

Nuku Nuku's personality reflects her feline origins, displaying behaviors like chasing mice, napping in sunlight, favoring fish-based foods, and reacting with instinctual excitement to stimuli like motor oil. She exhibits a consistently cheerful, optimistic, and innocent demeanor, often misunderstanding human social conventions yet remaining polite and kind-hearted. Her primary motivation is unwavering devotion to Kyusaku (whom she calls "Papa-san") and Ryunosuke, driving her to protect them at all costs. This protective instinct manifests fiercely against threats, though she rarely expresses deep anger. Her naïveté and physical power sometimes cause accidental property damage.

Her relationships center on the Natsume family dynamic. She views Kyusaku as a beloved creator/father figure and Ryunosuke as a cherished younger brother, striving to reunite the estranged family despite their conflicts. Akiko Natsume, Kyusaku's ex-wife and CEO of Mishima, alternates between antagonist and reluctant ally; she relentlessly pursues Nuku Nuku to reclaim Ryunosuke and the android technology, deploying agents like Arisa and Kyōko or experimental weapons, yet occasionally collaborates with Nuku Nuku against greater threats. Arisa and Kyōko, Akiko's subordinates, develop a persistent rivalry with Nuku Nuku due to repeated failures in capturing her, often suffering comedic defeats. Eimi Yoshikawa, another android modeled after her creator's granddaughter, becomes a recurring adversary fueled by jealousy and instability, obsessively seeking to transfer her consciousness into Nuku Nuku's body but lacking a viable method.

Character depictions vary across continuities. In the original manga and OVA (1992–1993), as well as the 1998 TV series, she appears as a 14–16-year-old girl integrated into high school life. The TV series amplifies comedic elements and school misadventures while reducing Akiko's role. In contrast, the *DASH!* OVA (1998) reimagines her as "Atsuko Higuchi," an amnesiac prototype android with a more mature 19-year-old appearance, light green hair, and biological systems like blood circulation. Here, Kyusaku is not her creator but a protector assisting her against Mishima, while teenage Ryunosuke develops romantic feelings for her. She activates a "tactical mode" when protecting lives, gaining public recognition as "Super Dynamite Girl." This iteration also introduces a twin counterpart designed to eradicate life, positioning Nuku Nuku as the failsafe countermeasure.