"The only thing that doesn't feel realistic in this series is Azumi's godlike speed."
Not the unbendable or unbreakable blade? So far Ichigeki is the only manga in which they actually teach people to throw away sword and replace it with fallen enemy's.
She is not a samurai, not even a sword fighter. She is a trained killer, that is why she is better than the others. No waste moment + being acrobatic can be a deathly combo IMO.
Not sure about other weapon but when it come to sword, Japanese way of fighting has too much ceremony in it. At least as far as my knowledge and experience go.