At the end of the Edo dynasty (10 years before, the series takes place). There was a man in Kyoto, named Hitokiri Batousai, he was known as the best swordsman, who helped establish the new dynasty, Meiji. Around that same time, Hitokiri Batousai, disappeared from the history books for good, after a disappearance, it was said that he killed what he shouldn't have. Nobody knew where he went.
10 years later, Himura Kenshin, showed up in Tokyo, he traveled the country, helping people, to try and repent for the crimes he committed as Hitokiri Batousai. He fights with a sakaba sword (a sword with an upside down blade). And he has sworn never to kill again.
When he got to Tokyo, he met, Kamiya Kaoru, and he decided to protect her. He also met some friends there, whom he also chose to protect.
Kenshin does not want to be known as Hitokiri Batousai, he gave up that title, when he left Kyoto. No matter how much he dislikes it, he will always be known by his enemies, and some of his peers as Hitokiri Batousai.
He has a nice personality, and does not like using violence, he uses the sword only to protect.
He is a master of Hiten Mitsurugi Ryu, the most powerful sword style.
He can be quite clumsy, at times, and in those spills of clumsiness, he usually says "oro", and his eyes go into spirals.
If you ever get a chance to see Rurouni Kenshin, I strongly suggest that you see it.