Who was Kawakami Gensai?

Kawakami Gensai (December 25, 1834 – January 13, 1872) was a retainer of Kumamoto domain and one of the four hitokiri of the Bakumatsu, the era’s named assassins. Watsuki has documented the debt directly: the model is credited to Gensai in the manga’s own first volume. The parallels are structural: a swordsman of slight, almost delicate build whose speed made him lethal in daylight, in an age that then had no use for him.

Gensai’s one confirmed assassination was famous: on August 12, 1864, in broad daylight in Kyoto, he killed the scholar-statesman Sakuma Shōzan with a single stroke, and is recorded telling his confederates afterward that it was the first time he had truly felt he had killed a man, because Shōzan was the greatest man of the time. He fought for Chōshū in Takasugi Shinsaku’s Kiheitai, survived the revolution, and was then arrested by the Meiji state he had helped create, on a harbouring charge, and executed in Tokyo in 1872, aged 37.