Come on guys, Mizuki isn't that hard.
I've beaten her with all the characters, even earthquake.
For Genjuro here's a golden tip.
Fierce Jumping Slash on Mizuki, when you land emediatly push medium slash to cover your ass or she will throw you. Try not to jump backwards or she'll use that white exploding energy ball on you. Instead doubleclick backwards with your stick to go faster backwards and still on guard.
Using this technique i defeat Mizuki within 25 seconds, that's even good enough for a fastest kill bonus. And there is a good chance you will be able to get her dizzy once in each round. Forget any light crap when she is dizzy, take the strongest slash possible, because she does not hae mercy with you either <IMG SRC="smilies/smile.gif" border="0">
hope this helps
LastResort