In the 23rd century, it is no longer necessary to work thanks to the latest technology. Convicts do the work that still needs to be done. The World Leisure Center uses a computer system to decide how people spend their free time. World citizen number DARK 7035 7201 is called Prun. Although an examination shows that his IQ is too low for him to have a child of his own, he becomes the father of Botho. Because it is a "black birth", he has to keep Botho hidden from now on. Prun comes into contact with the so-called "semi-intelligentsia", who oppose the government.