Enishi Yukishiro is the primary antagonist of the Jinchū arc, serving as the vengeful younger brother of Yukishiro Tomoe. His entire existence is shaped by the traumatic death of his beloved sister, whom he witnessed being accidentally killed by her husband, the former Hitokiri Battōsai, Himura Kenshin. This childhood trauma was so profound that his hair, originally black, turned permanently snow white from the overwhelming stress and grief.

Driven by an obsessive and consuming hatred, Enishi swore to enact Jinchū, a form of divine judgment or punishment from a person, against Kenshin. However, his goal was not simple murder. His intention was to systematically destroy everything Kenshin held dear, thereby plunging him into the same living hell of loneliness and despair that Enishi himself had endured after losing Tomoe. To achieve this, he spent a decade in China, rising to become a powerful overlord in the underworld and amassing both wealth and influence. He later returned to Japan and assembled the Six Comrades, a diverse group of individuals who also harbored grudges against Kenshin, to assist him in his elaborate scheme.

In terms of personality, Enishi is a complex character who often presents a facade of calm and polite happiness, a mask he uses to interact with his allies and manipulate situations to his advantage. Underneath this veneer, he is deeply unstable, wrathful, and ruthless, with his entire psyche revolving around avenging his sister. He suffers from persistent hallucinations or memories of Tomoe, believing he must act to earn her smile, which serves as the twisted moral compass for his actions. When his plan seems to be succeeding, he is filled with a cold glee; when it falters, he is prone to fits of madness and violent physical convulsions, such as when he attempted to strangle Kaoru, a reaction born from the deep-seated trauma of his sister's death.

Enishi is a phenomenally skilled swordsman, possessing a level of ability that makes him a match for Kenshin. He is a master of his self-taught fighting style known as Watōjutsu. This unique style blends the speed and slashing techniques of Japanese kenjutsu with the strength and fluidity of Chinese sword arts, wielding a distinct Chinese-made Japanese tachi known as a Watō. This style is almost perfectly designed to counter the techniques of Kenshin's Hiten Mitsurugi-ryū, allowing Enishi to block or evade attacks that would fell any other opponent. His most fearsome ability is the activation of his Frenzied Nerves. In this state, his nerves bulge throughout his body, heightening his senses to a superhuman degree and granting him explosive speed and strength. However, this power has a critical weakness, as it also makes him painfully sensitive to stimuli and, in a state of extreme rage, opens his defense to a precise counter-attack.

Throughout the story, Enishi's primary role is to systematically dismantle Kenshin's new life. He and his comrades first attack Kenshin's friends and allies. This culminates in a direct confrontation at the Kamiya Dojo, where Enishi defeats Kenshin. To deliver the final blow of his psychological revenge, he uses a life-sized doll crafted by his comrade Gein to create the illusion that he has killed Kenshin's beloved Kaoru. This act successfully drives Kenshin into a state of catatonic despair, fulfilling Enishi's goal of making him suffer.

His key relationships are few but intensely defining. His love and devotion to his sister Tomoe are the sole driving forces behind his life, a bond forged by her being his primary caregiver after their mother's death. His relationship with Kenshin is that of a brother-in-law turned mortal enemy; he despises Kenshin not just for the killing blow but for supposedly stealing Tomoe's happiness and then ending her life. His dynamic with Kamiya Kaoru is more complex; he sees her as the object he must take from Kenshin to complete his revenge, yet his deep psychological trauma prevents him from directly harming her, as her image blurs with that of his sister in his fractured mind. He orders the replica to be made for this reason.

Enishi's development in the arc is one of tragic collapse. After his successful Jinchū, he expects to see Tomoe's approving smile in his memories, but instead finds her frowning, suggesting his actions do not have her blessing. In the final duel on his island hideout, his rage allows him to access his Frenzied Nerves state, but he is ultimately defeated by Kenshin, who has found a new will to live. After Kenshin spares him and even thanks him for saving Kaoru, Enishi's psychological walls finally break down, and he openly weeps for his sister, consumed by grief and regret. He is later arrested but escapes, wandering to a remote village where his estranged father finds him, a broken man with nowhere left to go.