At one point in the film Giju (portrayed by Tomosaburô Ii) holds out his pinkie finger to another character. This is a Japanese hand gesture signifying that he is talking about a man's girlfriend, mistress or wife.
The Daruma appears throughout the film. Daruma is considered to be talisman of good luck to the Japanese. They are also seen as a symbol of perseverance and are often seen as gifts of encouragement.
The samurai in the guard station all carry two blades. This practice was known as daisho (literal translation: big-little). The larger blade was the longer and curved katana, generally used for combat and duelling. While the shorter blade; which would have been used for seppuku, was called the tanto.
In the film they refer to a character receiving a hook and being promoted to constable. This refers to the Japanese jitte, which translated means 'ten hands', and was a weapon carried by police in the Edo Period of Japan.
Zatoichi's katana is a shikomizue. This is a sword which is concealed within a wooden cane, thus the cane itself is both handle and scabbard.