Kaori Makimura, originally Kaori Hisaishi, is the adoptive sister of Hideyuki Makimura and eventual partner to Ryo Saeba after Hideyuki’s demise. Her early life was shaped by her parents’ divorce and upbringing under her father, Junichi Hisaishi, whose criminal pursuits ended in a fatal car chase. Adopted by Hideyuki’s detective father—who had once pursued Junichi—she joined the Makimura family, learning during junior high that her bond to Hideyuki was not biological.

Initially oblivious to Hideyuki’s shift from police duties to working as a "sweeper" with Ryo, Kaori wrongly accused her brother of murder until Ryo revealed the truth. After gangsters killed Hideyuki, she inherited his Smith & Wesson Model 36 revolver, later altered by Ryo to fire only in self-defense. Training under Umibozu honed her skills in crafting lethal traps with explosives, tripwires, and wooden stakes.

Tomboyish yet shrewd, Kaori favors masculine clothing and short hair, often sparking comedic gender confusion. Though fiercely clashing with Ryo over his womanizing—armed with a mallet or bazooka—she hides unspoken affection for him. Subtle developments hint at mutual feelings, culminating in a marriage implication by the manga’s end.

In *Angel Heart*’s parallel timeline, Kaori dies in an accident, her heart transplanted into assassin Xiang Ying (Glass Heart). Her spirit lingers through visions, guiding Xiang Ying to Shinjuku and interacting with figures like Umibozu and Miki. This storyline examines her enduring influence on Ryo and others, maintaining her posthumous role as a moral anchor.

Her biological sister, Sayuri Tachiki, briefly seeks reunion but ultimately honors Kaori’s loyalty to Ryo. A former nursing student, Kaori’s medical skills emerge in *Angel Heart*, recalling her life-saving aid to Ryo after a gunshot wound. Across adaptations, she evolves from a mourning sibling to a skilled ally and symbolic protector, blending humor with emotional depth.