On planet Amoi, a great society has developed, creating a computerized city called Tanagura, ruled by supercomputer Jupiter. The populace is almost entirely male and is based on hair color; anyone silver/blond are the elite, with dark/black hair as the bottom of society, often known as "mongrels". Blonds have "pets", which are usually young boys kept for a few years, who are especially made for performing sexual actions for the Blond's voyeurism entertainment. The pets are not supposed to be kept for long, nor are Blonds allowed to interact sexually with them; but one Blond, named Iason Mink, has kept a pet for years. Mink is also rumored to sleep with his pet named Riki and refuses to let go of him; despite Jupiter's disapproval. Riki fights with his emotions and society problems, unable to decide what to do about his old friend/lover Gai (Guy) and their gang. Iason is obsessed with keeping Riki, and Riki doesn't know what to do; fight against him or surrender to him.

Riki returns to Iason Mink to live as his "pet," but Riki's friend Guy tries to take him back.