In the near future, the population has been decreasing due to global warming caused by abnormal weather. People have chosen to coexist with androids, leaving their labor to them. In such a world, four androids challenge “Babel,” an entertainment tower where they earn prizes for singing and dancing. Without an owner, they aim to reach the top of “Babel” as KNOCC, and gradually grow up by meeting a boy genius named Esora. Then, an event triggers a special program called “kokoro” within the four of them...?