Hitokiri Gensai was a renowned Assassin during the 1860's, most well known for cutting down Sakuma Shozan in broad daylight with a single stroke. He was said to have been feminine in appearance, although his outward appearance and his inner were vastly different.
I study Iaido, and Kendo, and have since i was a little girl, being that i favour Iai over Kendo, i was called Gensai as a kid because of my ability in iaido demonstration, which was supposedly Gensai's style of swordsmenship, although being that he died in 1871 with no heir, its not sure exactly what his sword art was. Gensai was said to have studied under Todoroki Buhei, but records of the period were stark at best.
It should be remembered that this was a period of unrest and revolution and many small details were forgotten or left unsaid.