Tokiko “Key” Mima is a 17‑year‑old robot living in the quiet Japanese countryside. When her grandfather, Dr. Murao Mima, dies, he leaves her a dying wish: she can become a real girl if she makes thirty‑thousand friends. Determined to fulfill this promise, Key leaves the tranquil Mamio Valley for the bustling streets of Tokyo, where she reunites with her childhood friend Sakura Kuriyagawa. There she becomes enamored with the idol singer Miho Utsuse, hoping that a career in music will help her amass the friends she needs. Yet Miho hides a dark secret, she is connected to Jinsaku Ajou, an old rival of Dr. Mima who seeks a new breakthrough in robotic weaponry. As Key pursues her goal of becoming human, Ajou initiates a dangerous plan, revealing that Key harbors far more than meets the eye.