Kuroi Sabato is a member of the Itto-ryu sword school in Blade of the Immortal. He trained under Anotsu Saburō, the grandfather of Itto-ryu leader Anotsu Kagehisa, and became a highly skilled master of the style. His most defining trait is a profound obsession with preserving youthful beauty. This fixation manifests in a horrifying practice: he decapitates women he becomes infatuated with, treats their heads through taxidermy, and then sews the preserved heads onto his shoulders, believing he can keep their beauty unchanging forever. His victims include his former wife and the mother of the story's central figure, Rin Asano.

His personality is marked by a blend of poetic flourish and sadistic cruelty. He composes verses that allude to the band Black Sabbath, a quirk that accompanies many of his appearances. His very name is a direct reference: Kuroi translates to black and Sabato, when romanised, resembles Sabbath, an homage by creator Hiroaki Samura to one of his favourite musical acts.

In the period before the main narrative, Kuroi Sabato was entrusted with killing Kurose, Rin’s father, and he carried out that task personally. For two years afterward, he sent love letters to Rin every night, a predatory gesture that would eventually draw her and her bodyguard into a confrontation. When Rin and the immortal swordsman Manji devise a plan to meet him, Kuroi Sabato serves as an early antagonist whose brutality establishes the dangerous world they navigate. He is defeated and killed by Manji during that encounter, an event that sets off further reprisals from the Itto-ryu.

Key relationships beyond his victims are limited. He stands as a respected, if feared, pupil within the Itto-ryu hierarchy, and his connection to Rin is defined entirely by violence: he murdered her mother, preserved and displayed her mother’s head on his body, and murdered her father. There is no suggestion of redemption or deep internal change. He remains a static figure of grotesque fixation whose role is to embody the extreme depravity that Rin and Manji face early in their journey.

In combat, Kuroi Sabato is a master swordsman of the Itto-ryu tradition. Alongside his sword, he wields a pair of shuriken known as Karasu, or “The Crow.” His fighting ability and his macabre shoulder-mounted heads make him an unsettling and dangerous opponent. His death at Manji’s hands does not occasion any development in him, but it does catalyse the ongoing conflict between Rin, Manji, and the Itto-ryu.