Tokiko “Key” Mima is a robot in the form of a lifelike 17-year-old girl, who lives with her automaton-expert grandfather. When her grandfather dies, he leaves behind a final message explaining that Key must complete the task that he could not: to make her fully human. To do so she must accrue the power of 30,000 friends. Since her home of Mamio Valley is nowhere near populous enough, she goes to Tokyo, where she runs into Sakura, her former best friend who had moved away years earlier. After seeing top idol Miho Utsuse perform, Key decides that the solution to her problem is to become an idol herself. Though incredulous at first, both Sakura and her love interest Shuichi Tataki (who is also Miho's fan club president) eventually come to support Key in this endeavor.