Catching up on my C&C in a spare thirty seconds....
All in all, this is quite good... but I had major problems with the
treatment of Cologne. The evil, ruthless schemer that she's portrayed as
here is very fanfic cliche and not really consistent with her treatment
in the manga. While she's shown that she will go after targets of
opportunity (the reversal jewel), she really didn't make much of an
effort at all to win Ranma over after her first couple of storylines.
Unless there's some new development, it's hard to see her doing what she
does here.
I suggest humanizing your treatment of Cologne and giving her some
additional motivation if you want to keep her as the source of the
poison. When a character makes a major change of behavior, there has to
be a major reason for it, and you need to show us what that is.
In general, when writing a character that you haven't written before,
reading back over his/her appearances in the manga is a good idea. Then
if you decide your story is well-served by a different treatment, that's
fine -- as long as it's deliberate and not because you've been led by
fanfics into thinking that the character really is like that.
Looking forward to reading more....
Gary Kleppe
http://www.execpc.com/~kleppe/comics.html