In 1868, after the end of the Bakumatsu war, the former assassin Kenshin Himura promises to defend those who need without killing and wanders through Japan with a sword with inverted blade during the transition of the samurai age to the New Age. When Kenshin helps the idealistic Kaoru Kamiya from the gangsters of the powerful opium drug lord Kanryuu Takeda that wants her school for his production of opium, Kaoru invites Kenshin to stay in the school. But the drug chemist Megumi Takani escapes...