When inventor Kyusaka Natsume transfers the brain of his son Ryunosuke's cat into a top secret android body, the family doesn't lose a pet... they gain a daughter! While she may look like a typical teenage girl to the rest of the world, Nuku Nuku's feminine exterior hides the superhuman strength and abilities of the NK-1124 android chassis, making her the most potent fighting force ever unleashed upon unsuspecting Japan... and the ideal bodyguard for Ryunosuke! But can even Nuku Nuku keep her young charge out of the insidious clutches of the ruthless Akiko Mishima, president of Mishima Heavy Industries, financier of the NK-1124 project, Kyusaku's ex-wife and Ryunosuke's mother? the greatest custody battle of all time erupts in a conflagration across Japan as Akiko unleashes the full force of M.H.I.'s military products division, manned by her elite team of Office-lady Warriors, in her bid to win back Ryunosuke.