[Cosmic Eagle]

Originally Posted by falcolobo

The weight of the sword adds extra weight, so a faster movement due to the sword falling, and thus fast movements, also the difference between a katana and a butterfly knife is pretty large. Still, its an anime/manga/light novel. Somethings may be, well, fictional?

And yeah, Samurai normally used bows, katanas were secondary up untill the Fedual lords became more powerful. Katanas are pretty heavy, though lighter than broadswords, they still are pretty heavy. So for it to be effective in battle the samurai has to be strong.

Also

Spoiler for Further Kinji Techniques:

Is it possible for his Irokane Butterfly Knife to make him use a chotei ability?

Why do you say the balisong is Irokane? It's more likely that Shirayuki's sword is or Durandal...