The Complete Guide to Anachronisms in Samurai Champloo--
Lullabies of the Lost (Verse 2)/Idling One's Life Away (the second verse)
Episode 17: Lullabies of the Lost (Verse 2)/Idling One's Life Away (the second verse):
Okuru's repeater crossbow. Seen in #16 but I thought I'd save it to discuss here. This is a large, qualified maybe for the following reasons: (a) Repeater crossbow technology was solidly established in China at the time and had been since 250 BCE; even the earliest recorded design (the Chu-ko-nu or Zhuge-nu) could fire one bolt per second and by the 13th century they had refined repeaters that could fire ten bolts in 15 seconds, some two bolts at once. BUT: (b) I can't find anything to date the arrival of the crossbow in Japan, and more to the point (c) I can't find any evidence that the Ainu ever used the crossbow at all. They were highly skilled archers and there are tons of examples of their longbows, quivers and arrows, but though they used a crossbow-type mechanism in animal traps, I can't find anything suggesting that they had or used the crossbow as a weapon. So my assumption is that while the crossbow may not be traditionally used by Ainu, Okuru, who traveled a good deal and was almost certainly an experienced archer, picked up the crossbow at some point in his travels and, finding it effective, took to using it in preference to the longbow.
A useful link on the chu-ko-nu Chinese repeater.