According to Quentin Tarantino, Sonny Chiba's character, Hattori Hanzo, is meant to be the most recent descendant of his character(s) from "Hattori Hanzô: Kage no Gundan" (1980), a Japanese Television Series. The series was done in multiple various installments, in which Chiba would play Hanzo a generation removed from the previous installment.
1541 - 1596
Tokugawa retainer and reputed 'ninja' leader
Also known as Masashige. The son of a certain Hattori Yasunaga, Hanzo, who would earn the nickname 'Devil Hanzo', served Tokugawa Ieyasu loyally and usefully. His nickname - Devil Hanzo - was not only to pay homage to his skills but also to distinguish him from another Tokugawa 'ninja', Watanabe Hanzo. Hattori, who fought his first battle at the age of 16, went on to serve at Anegawa (1570) and Mikatagahara (1572), but his most valuable contribution came in 1582, following Oda Nobunaga's death. At that time Tokugawa and his retainers had been staying near Ôsaka and learned of the assassination only just in time to avoid being detained by Akechi Mitsuhide's troops. But they were by no means out of the woods. Mikawa was still a long way away, and Akechi men would be combing the roads for them. At this point, Hanzo suggested that they take a route through Iga province, as he had ties with the samurai there. In addition, Ieyasu had sheltered survivors from Nobunaga's bloody invasion of that province in 1580 and those who knew of this would certainly be well disposed to offer assistance. Honda Tadakatsu sent Hanzo on ahead, and, as hoped, the Iga men agreed not only to guide them along back roads, but also to provide them with an escort. At length, Tokugawa and his band returned to Mikawa safely. The same could not be said for Anayama Beisetsu, a recent Tokugawa addition who had insisted on taking a different route.
Hanzo was succeded by his son, Masanari, who would be given the title Iwami-no-Kami and whose men would act as the guards of Edo Castle. Hanzo's reputation as a ninja leader who commanded a 200-man strong unit of Iga men has grown to legendary proportions.