wow. I thought saito's team was made up.
Kawakami Gensai (河上彦斎, 4 December 1834 - 13 January 1871), was an imperialist and one of the four great Hitokiri (lit. "man-slayer") of the Bakumatsu period of 19th century Japan, and fought against the Western-accommodating Tokugawa Shōgunate in order to restore the Emperor to power and force all foreigners from Japan. It is said that, at first glance, he could be mistaken for a girl or young boy, but that his nature was indeed the complete opposite. He was recorded as being a cold, disciplined, and calculating warrior. It was also said that he was the most lethal of the four Hitokiri.
Kawakami was a non-practicing Buddhist, but dedicated himself to its study heartily. His discipline was Kenjutsu. He studied the “lighting-fast” Furanui style, and used Shiranui-ryu. Kawakami was a loyalist and patriot of the Empire, who, at the time, were called the “Ishin Shishi” group. Because of these beliefs, and his personal strengths in the area of swordsmanship, he became a Hitokiri, or elite samurai assassin, who served the Emperor vehemently.
Kawakami was made more famous for cutting down Sakuma Shōzan, a prominent, pro-western Japanese politician in broad daylight. He was the presumed suspect for many other prominent assassinations, but nothing had ever been proven, and still remains a mystery even to date. After the Meiji restoration ended the era of the samurai, Kawakami taught samurai philosophy for a short time. However, his ideas about isolationism conflicted with those of the government. He was brought in on falsified charges, and executed in the fourth year of the Meiji era (1871).
The character Himura Kenshin from the anime and manga Rurouni Kenshin/Samurai X was loosely based on Kawakami.