Reileen Kawahara is the sister of Takeshi Kovacs.
Reileen was born on Harlan's World and is of mixed Japanese and Eastern European decent. She has one older brother, Takeshi Kovacs. During their childhood, Rei and her brother grew very close living under their abusive father, often exploring the planet's wilderness together and telling scary stories like the Patchwork Man. Eventually, following the death of their mother, Takeshi was forced to kill their Father after he threatened to harm Rei. Taken into custody, Takeshi joined the Colonial Tactical Assault Corps in the belief that his sister would be taken care of. Instead, Reileen was sold to the Yakuza and became one of their enforcers. During a CTAC raid, Reileen met Takeshi for the first time in ten years. During the reunion, CTAC officers tried to kill Rei, prompting Takeshi to turn on them to protect his sister. Reileen did the same for Takeshi, turning on her Yakuza masters.
Now fugitives from both factions, Rei and Takeshi fled to the wilds of Harlan's World, falling in with Quellcrist Falconer and her Envoys. While Takeshi became dedicated to the cause, Reileen was less enthusiastic. Out of jealousy for Quell, Rei ultimately betrayed the rebels to the Protectorate and turned on Quell herself during the escape, destroying their shuttle with an orbital laser strike. Though presumed dead, Rei had actually managed to survive the explosion, using her new wealth to become one of the most powerful meths by 2384.
Throughout the series
Reileen personifies the worst traits of a meth, and all the qualities that Quellcrist Falconer warned about. She is arrogant, manipulative and self centered, with a massive ego and "love" for her brother that verges on the psychotic and possibly incestuous. She believes she has made herself stronger and better by getting rid of things she sees as weak- mainly empathy, compassion and human emotions. As a consequence, however, she is somewhat ignorant in certain matters; She claims to love her brother, but does not seem to grasp what love means and the bonds that it can form, as Takeshi had done with allies past and present.
Reileen Kawahara, in the book the series was based on wasn’t Kovacs’ sister. Hence their different surnames.