In 1868, during the violent final days of the Bakumatsu era, a shadowy assassin known as Hitokiri Battosai fights for the Imperial side, slaughtering his enemies without mercy to help bring about the end of the shogunate and the dawn of the Meiji Restoration. After the decisive battle of Toba-Fushima, the legendary killer disappears, his fearsome reputation becoming little more than a ghost story.

Ten years later, a wandering swordsman named Kenshin Himura arrives in Tokyo during a time of rapid Westernization and social upheaval. He is a quiet and gentle soul, carrying only a sakabatō, a uniquely crafted sword with the blade on the reverse edge, making it nearly impossible to kill with. He has taken a solemn, unbreakable vow to never take another life, instead dedicating himself to protecting the innocent as atonement for the blood he has already spilled.

Kenshin soon encounters Kaoru Kamiya, a spirited young woman and the instructor of her late father’s kendo dojo, the Kamiya Kasshin-ryu. The dojo is under threat from gangsters working for Kanryū Takeda, a ruthless and wealthy opium drug lord who wants the land for his operations. Kenshin easily defeats the thugs, and Kaoru, recognizing his honorable nature despite his strange appearance, invites him to stay at the dojo.

Kenshin’s peaceful existence is immediately complicated. A mysterious murderer is terrorizing Tokyo, slaying police officers and leaving behind calling cards with the name “Battosai.” This forces Kenshin to confront the dark legacy of his past, as the public and the authorities begin to believe the legendary assassin has returned. The situation escalates when a beautiful and haunted woman named Megumi Takani seeks refuge at the dojo. She is a talented chemist who was forced by Kanryū to produce a highly addictive form of opium and is now fleeing from his grasp.

As Kanryū uses his private army of former samurai and a deadly weapon to pressure Kaoru into surrendering her dojo, Kenshin finds he cannot remain on the sidelines. He is joined by Sanosuke Sagara, a brawling former sekihōtai (a rebel militia soldier) who wields a massive zanbatō sword and holds a grudge against the new Meiji government. Together, they fight to protect the dojo and its residents.

The central conflict brings Kenshin face to face with a terrifying specter from his past: Jin-e Udo. A fellow former assassin who revels in bloodshed, Jin-e is the one impersonating Battosai, and he is obsessed with forcing Kenshin to abandon his pacifist vow and return to his true nature as a killer. Jin-e possesses a hypnotic ability that can paralyze his opponents with fear, making him a formidable foe.

In a desperate attempt to shatter Kenshin’s resolve, Jin-e kidnaps Kaoru. The final confrontation takes place in a secluded forest, where Kenshin is forced into a brutal psychological and physical battle. Jin-e’s taunts dredge up the deep guilt and self-loathing of Kenshin’s past as an assassin. Pushed to the edge to protect Kaoru, Kenshin nearly succumbs to his killer instincts and delivers a potentially fatal blow. Before Kenshin can complete the act, Jin-e, satisfied that he has momentarily revived the Battosai, takes his own life.

Having rescued Kaoru and revealed the full, horrifying truth of who he once was, Kenshin expects rejection. However, Kaoru accepts him for the man he is trying to become, not the demon he left behind. With the immediate threat gone, the former wanderer finally finds a sense of home at the Kamiya dojo, though he knows his past will continue to haunt him.