Ai no Kusabi Series by Reiko Yoshihara

In the future, on a distant star lives a new society. Ruled by a computer system named Jupiter, men are divided into classes based on their hair color. The Blondies, genetically altered by Jupiter, are the highest class and occupy the capital city of Tanagura. Those with black hair, Mongrels, are forced to live in the slums, Ceres. Iason, the leader of the Blondies, encounters Riki, a mongrel, in the streets of Ceres one night and sets out to own him... moreIn the future, on a distant star lives a new society. Ruled by a computer system named Jupiter, men are divided into classes based on their hair color. The Blondies, genetically altered by Jupiter, are the highest class and occupy the capital city of Tanagura. Those with black hair, Mongrels, are forced to live in the slums, Ceres. Iason, the leader of the Blondies, encounters Riki, a mongrel, in the streets of Ceres one night and sets out to own him.---Taken from back cover:The Man's upturned blue eyes were so unimaginably beautiful that they could make anybody tremble with awe. In this moment, however, they also glimmered with an icy fire--perhaps revealing the fury of his wounded pride, or rather, a manifestation of his uncontrollable obsession.Ceres: a city without ethics or taboos, ruled by instincts and lusts. These are the slums--immutable, eternal, home to those poor, caged souls stricken with a perpetual melancholy.After three years, Riki unexpectedly returns to Ceres, but all is not well. The "Charisma" of the slums is a changed man. Faced with growing suspicion that he's lost his spark, and haunted by the memory of what happened during those three years away from the slums, Riki finds himself pulled into the escalating gang warfare as rivals attempt to wipe out his pack before they can regroup under their newly-returned leader. And then there is the frighteningly cold, regrettably familiar man he meets by chance one day: the beautiful Iason Mink. What secrets lie behind the smile of that bewitching Blondy? less

Released from Iason's curse, Riki is spending his days idly in the slums when he's drawn into a trap - is it a secret plot of uninvited visitor Kirie, or could it also be a cruel way to force Riki to choose between the body of his old roommate Guy and his own pride? Riki revives the memories of his three years of lust and masochism with Iason. Is freedom just an illusion?

After his release from house arrest and return to the slums, Riki's relationship with Guy has been awkward at best. Before they are able to resolve any of their relationship issues, the security forces of the notorious Midas cross the border for an all-out invasion. Can anyone survive the attack of such powerful forces?