The story is set in the future on the planet named Amoi which is controlled by a supercomputer named Jupiter. Among the mostly male human population, the light-haired elite class is allowed to temporarily keep the dark-haired "mongrels" as pets. One elite member, Iason, encounters a mongrel named Riki in the slums and decides to take him in. However, Iason keeps Riki longer than it is socially approved, and rumors abound about their possible relationship.

The story is set in the future on the planet named Amoi which is controlled by a supercomputer named Jupiter. Among the mostly male human population, the light-haired elite class is allowed to temporarily keep the dark-haired "mongrels" as pets. One elite member, Iason, encounters a mongrel named Riki in the slums and decides to take him in. However, Iason keeps Riki longer than it is socially approved, and rumors abound about their possible relationship.