Kenshi Himura, known originally as Shinta, is the central figure of his narrative, a man whose life is defined by the profound contrast between his past as a ruthless assassin and his present as a gentle wanderer. Born in 1849, he was orphaned at a very young age when his parents died of cholera. After being sold into slavery, the three women who cared for him were killed by bandits, a tragedy from which he was rescued by a powerful master who would rename him Kenshin, meaning "Heart of the Sword," and train him in the deadly Hiten Mitsurugi-ryu sword style. Under this master, he grew from a helpless child into a skilled swordsman, but his idealistic desire to end the turmoil of the Bakumatsu period led him to leave his training and join the Ishin Shishi as a political assassin. As the feared Hitokiri Battousai, he killed without remorse, believing that taking lives could bring about a new era of peace. However, a tragic encounter with a woman named Yukishiro Tomoe, who first sought to avenge her fiancé but ultimately fell in love with him, changed the course of his life. In a fateful confrontation, Kenshin accidentally killed Tomoe, who stepped in to save him, and with her dying breath, she gave him the second scar on his cheek, completing the cross-shaped wound that would forever mark him. Consumed by guilt and grief, he made a sacred vow never to take another life.

In the years following the Meiji Restoration, Kenshin wanders the countryside as a rurouni, a masterless samurai, seeking atonement for his past sins. Physically, he is described as having a slim build, below-average height, an androgynous face, and long red hair tied in a ponytail, which makes him appear harmless and unassuming. His most distinctive feature is the prominent cross-shaped scar on his left cheek. His clothing is simple and worn, typically a red kimono over a white hakama. In stark contrast to his terrifying reputation, his demeanor is soft-spoken, humble, and almost childishly naive, often ending his sentences with the formal and polite "de gozaru". He is frequently flustered and will utter his trademark exclamation, "oro," when surprised or confused. Despite his gentle nature, a shift occurs when his resolve is tested; his eyes take on a sharp, amber glow, and his presence becomes overwhelming as his latent killer instincts, the Battousai, briefly resurface to face a threat. His core motivation is to protect the innocent and help those who suffer right before his eyes, as a way to repay the debt of the lives he took. He embodies the philosophy of a katana that protects, rather than one that kills, and he adheres strictly to his vow by wielding a sakabatō, a reverse-blade sword with the cutting edge on the opposite side, making it nearly impossible to fatally slash an opponent.

Kenshin's journey is heavily shaped by the relationships he builds after arriving in Tokyo. He meets Kamiya Kaoru, the young head of a kendo dojo, who is initially targeted by someone impersonating the Battousai. After seeing his skill and learning of his past, she offers him a home at her dojo, becoming his anchor to a peaceful life and eventually his wife. Through her, he is joined by Myojin Yahiko, a spirited young boy from a fallen samurai family whom Kenshin mentors, and Sagara Sanosuke, a former brawler who becomes his best friend and loyal ally in battle. His past also catches up with him in the form of rivals who later become complex allies. Saito Hajime, his former enemy from the Shinsengumi, is a ruthless fighter with whom Kenshin shares a grudging respect. Shinomori Aoshi, the former leader of the Oniwabanshu, becomes obsessed with defeating Kenshin to prove his strength but eventually finds a new purpose. His primary antagonists include Shishio Makoto, his successor as the shadow assassin who threatens to plunge the new era into chaos, and later Yukishiro Enishi, Tomoe's younger brother, who seeks revenge for his sister's death.

Kenshin's character undergoes significant development as he reconciles his two identities. Initially, he struggles to suppress the Battousai completely, but over time, he learns to accept his past rather than run from it. He realizes that his strength as a swordsman is not solely derived from technique, but from his unwavering will to live for the sake of others, a stark contrast to his days as a hollow instrument of death. This personal struggle is often reflected in his fighting style, the Hiten Mitsurugi-ryu, which he mastered but ultimately chose not to pass on. His abilities are superhuman; he possesses god-like speed, capable of overwhelming multiple gunmen before they can fire, and displays incredible reflexes and combat intelligence. His arsenal of techniques is vast, ranging from rapid-strike attacks like the Ryusosen to powerful acrobatic slashes like the Ryutsuisen. The ultimate secret technique of his school is the Amakakeru Ryu no Hirameki, a super-fast battōjutsu draw so powerful that the first strike creates a vacuum to pull an opponent into an even more devastating second strike. However, the immense physical toll of these techniques, combined with his small frame, gradually wears down his body as the story progresses, limiting his ability to use his most powerful moves. Despite his incredible power, he remains committed to non-lethal combat, using the blunt edge of his sakabatō to defeat his enemies, believing that even the worst villains deserve a chance to live in the new era he helped create.