Tokiko Mima, called Key, is a robot. Since she was created by her 'grandfather', Dr. Mima, she has lived among humans. Now Dr. Mima is dead, and has left behind a cryptic last message: if Key can somehow get 30,000 people to feel for her, she can become fully human. However, Key's quest may not be so simple - for an ominous plot is being hatched by Dr. Mima's rival, Jinsaku Ajo.