Rurouni Kenshin: Meiji Kenkaku Romantan

"140 years ago in Kyoto,with the coming of the 'Black Ships', there arose a warrior called Hitokiri Battousai. Felling men with his blood stained blade, he closed the turbulent Bakumatsu era and slashed open the age known as Meiji. Then he vanished, and with the flow of years, became a legend. In the 11th year of Meiji, in the middle of Tokyo this tale begins..."
Rurouni Kenshin (the OAVs and Movie are known as Samurai X) tells the story of a wanderer named Kenshin, who used to be called Hitokiri Battousai (Hitokiri means Assassin) during the Japanese civil war, and is now trying to make up for his past and all his murders by helping those in trouble with his reverse-blade sword and by using his powerful technique called Hiten-Mitsurugi Ryu to battle oppressors of freedom and justice, yet struggling with himself and his own murdering self.
During the series Kenshin joins others in his quest: Kaoru Kamiya, a young orphan girl who became tutor of the Kamiya-Kashin Ryu Kendo style; Sanosuke Sagara, a mercenary who used to bear the name Zanza and fights just with his incredibly powerful fists; Yahiko Myojin, a young boy who was rescued by Kenshin from a band of thieves and now a pupil on Kaoru's dojo; and Megumi Takani, a female doctor who was rescued by Kenshin from a band which forced her to make a lethal drug. Together they all fight those who oppress the weak while they seek their destiny as well happiness and redemption.
The series is based on a homonymous manga created by Nobuhiro Watsuki, which was first published in 1994.