When Natsume Atsuko, nicknamed Nuku Nuku, comes to live with Ryounosuke's family, he falls in love instantly. After all, to all appearances, she's a beautiful, normal - if slightly ditzy - teenage girl. In reality, however, she's an all-purpose cat-brained andorobot who's escaped from Mishima Heavy Industries' research laboratories.

She's not supposed to use her special powers, but when more of Mishima's experiments run amuck and her friends are threatened, she'll do whatever she can to save them. It's never just another day at school when your classmate's an All Purpose Cultural Cat Girl!