Akihiro Tomikawa, who portrays Ogami Itto's son, Daigoro, only ever played this one character for his on-screen acting career. He appears as Daigoro in all six 'Lone Wolf & Cub' feature films, and then in 1980's 'Shogun Assassin', which is recut footage from the first two films in the series.
Footage from the first two Lone Wolf and Cub films (Sword of Vengeance and Baby Cart on the River Styx) from 1972 (Japan) would years later be re-edited into an American film called Henker des Shogun (1980). This merger of the two films would go on to earn its place in American pop culture as one of the most notorious exploitation films of the early 80s.
Ogami Itto is seen beheading those who wish to die by seppuku. Itto's role here is as a second, but the Japanese term for this is kaishakunin, and the act of beheading someone thus is known as kaishaku.
As can be seen in the film, samurai generally carried two blades. The katana was the longer of the two, and was most commonly used for combat and dueling. The wakizashi was the shorter of the two. It is unknown exactly what this was used for though it is believed to have been for cqc (close-quarters combat). This practice was known as daisho; which literally translates to 'big-little'. A third, the tanto, which was even shorter, was a blade or knife traditionally used for performing seppuku. Sometimes carried in addition to the main set.
This is the first of six films in the 'Lone Wolf & Cub' film series. All of which star Tomisaburô Wakayama as protagonist, Ogami Itto.